JP7680332B2 - Gas detector - Google Patents

Description

The present invention relates to a gas detector.

Some gas detectors have multiple types of sensors so that a single gas detector can detect multiple types of gas. One such gas detector is known to have multiple intake lines (flow paths) provided in the measurement chamber, with a gas sensor and a flow control valve installed in each line (see, for example, Patent Document 1). There is also a gas detector in which each flow path does not have its own gas inlet, but has multiple flow paths branching off from a common gas inlet, with each of the multiple flow paths having a sensor (see, for example, Patent Document 2).

Japanese Patent Application Publication No. 5-3142109 Japanese Unexamined Patent Publication No. 4-12608

In gas detectors, in order to perform highly accurate and precise detection, gas calibration of each sensor is performed periodically. In the gas detector described in Patent Document 1, when performing gas calibration of each sensor, each flow path in which a sensor is provided has an individual gas inlet, so that gas calibration for each sensor can be performed by flowing in a calibration gas for each sensor from the gas inlet of each flow path. However, in the case of a gas detector such as the gas detector described in Patent Document 2, in which each flow path does not have an individual gas inlet, but has multiple flow paths branching from a common gas inlet, and each of the multiple flow paths has a sensor, if a calibration gas is introduced from a common gas inlet, the same calibration gas will reach the multiple flow paths. As a result, the same calibration gas will come into contact with the sensors of all the flow paths, which is undesirable.

The present invention was made based on the above circumstances, and its purpose is to provide a gas detector that allows gas calibration of the sensor for each flow path, even if the gas detector has multiple flow paths branching off from a common gas inlet.

A gas detector according to the present invention is a gas detection device comprising a plurality of flow paths in which one or more sensors are interposed, a branch flow path connected at one end to a gas inlet and branching into two or more at the other end, a calibration gas flow path into which a calibration gas flows, and a flow path forming section in which the branch flow paths and the calibration gas flow path are formed, wherein the flow path forming section is configured so that the flow path forming section can switch between a state in which the plurality of flow paths are connected to the branch flow paths and a state in which the calibration gas flow path is connected to one of the plurality of flow paths, the gas detector comprises a case having the plurality of flow paths within the case, an opening of the branch flow path and an opening of the calibration gas flow path are formed on a joint surface of the flow path forming section with the case, openings of the plurality of flow paths are formed on a joint surface of the case with the flow path forming section, and the flow path forming section is configured so that the opening positions of the flow path forming section can be changed to switch the connections between the openings of the branch flow paths and the openings of the calibration gas flow path and the openings of the plurality of flow paths .

The gas detector of the present invention has multiple flow paths branching from a common gas inlet, and the flow path forming section is configured to be switchable to a state in which the calibration gas flow path is connected to one of the multiple flow paths. During gas calibration, the calibration gas flow path is connected to only one of the multiple flow paths, so that calibration gas can be introduced into only one of the flow paths.

The gas detector is preferably configured to include a case, have the multiple flow paths within the case, and have an opening for the branch flow path and an opening for the calibration gas flow path formed on a joint surface of the flow path forming part with the case, and have openings for the multiple flow paths formed on a joint surface of the case with the flow path forming part, and by changing the position of the opening of the flow path forming part relative to the case, switch between the connection between the opening of the multiple flow paths and the opening of the branch flow path and the connection between the opening of any of the multiple flow paths and the opening of the calibration gas flow path. In a gas detector having multiple flow paths branched from a common gas inlet as described above, there are various possible configurations for introducing calibration gas into only one flow path, but by configuring the flow path forming part so that the connection between the opening of the branch flow path and the opening of the calibration gas flow path and the opening of the multiple flow paths can be switched by moving the flow path forming part, it is possible to easily configure the gas detector.

Of the multiple flow paths, it is preferable that one of the flow paths is provided with a flow rate adjustment unit, and the other flow path is provided with a separate flow rate adjustment unit downstream of the branch point of the branch flow path corresponding to the other flow path. In this way, in the gas detector of the present invention, a flow rate adjustment unit is provided in one of the flow paths, and a separate flow rate adjustment unit is provided downstream of the branch point of the branch flow path corresponding to the other flow path, making it possible to quickly detect the occurrence of a gas leak at the connection when switching flow paths.

It is preferable that the flow path forming section is made of a disk-shaped disk portion, and the connection state is switched by rotating the disk portion on its center to change the position of the opening. By configuring the flow path forming section in this way, it is possible to easily switch the flow path.

The flow path forming part is provided with a protruding part for calibration gas, in which a calibration gas inlet communicating with the calibration gas flow path is formed, and the gas detector preferably has a cover that covers at least the protruding part for calibration gas, and an engagement part that engages with the protruding part for calibration gas when the cover is closed is formed on the inside of the cover. By forming such an engagement part, when the opening position of the flow path forming part is changed to switch the connection of the flow path, if the protruding part for calibration gas is not placed in the specified position by mistake, the protruding part for calibration gas cannot engage with the engagement part. This makes it possible to notify the user of a malfunction, for example, by not being able to close the cover. In this way, malfunctions when switching the flow path can be suppressed, and gas leakage caused by malfunctions can be prevented.

It is preferable that a sign portion is provided that indicates the position of the calibration gas protrusion during normal operation and during calibration operation. Since the sign portion can be visually confirmed, malfunctions when switching the flow path can be suppressed, and gas leakage caused by malfunctions can be prevented.

1 is a perspective view showing an outline of a configuration of a gas detector according to the present invention; 2 is a perspective view showing the gas detector shown in FIG. 1 with a cover in an open state. FIG. 2 is an exploded perspective view of the periphery of a switching portion in the gas detector shown in FIG. 1 . 2 is an exploded perspective view of a switching portion in the gas detector shown in FIG. 1 . 2 is a schematic diagram for explaining flow paths during normal operation in the gas detector shown in FIG. 1 . FIG. 2 is a schematic diagram for explaining flow paths during a calibration operation in the gas detector shown in FIG. 1 . FIG. 2 is a schematic diagram for explaining flow paths during a calibration operation in the gas detector shown in FIG. 1 . FIG. 2 is a plan view of a switching portion and its surroundings in the gas detector shown in FIG. 1 .

The following describes an embodiment of the gas detector of the present invention with reference to the drawings. Note that the terms "first", "second", and the like in this specification are used to distinguish one component from another, and are not intended to limit the number, order, or priority of the components. In this embodiment, the same components are distinguished by adding an alphabet after the number.

As shown in Figs. 1 and 2, the gas detector 1 includes a case 10 having a substantially cubic shape. The gas detector 1 also includes a cover 20 that covers the front surface 30 of the case 10. An opening 21 is provided at the top of the cover 20, and a display unit 31 provided on the front surface 30 of the case is exposed through the opening 21. The display unit 31 displays gas detection results and various messages. Note that the arrows indicating the up, down, left, right, and front-to-rear directions in Fig. 1 indicate the up, down, left, right, and front-to-rear directions in this embodiment.

The bottom surface 11 of the case 10 is provided with a gas inlet 12 and a gas outlet 13. As will be described in detail later, inside the case 10, a first flow path 51 (not shown in FIGS. 1 and 2) and a second flow path 52 (not shown in FIGS. 1 and 2) each equipped with a sensor are formed. The gas detector 1 in this embodiment is configured such that a common flow path 50 (not shown in FIGS. 1 and 2) from the gas inlet 12 branches into the first flow path 51 and the second flow path 52 each equipped with a sensor.

The cover 20 is supported by the case 10 at both ends of the bottom surface 11 of the case 10 via a rotating shaft 14. This allows the cover 20 to be freely pivoted about the rotating shaft 14 at the bottom end of the case 10, i.e., to be freely opened and closed. When the cover 20 is pivoted about the rotating shaft 14 to the open state, the front surface 30 of the case 10 is exposed as shown in FIG. 2.

A display unit 31 is provided at the top of the front surface 30. A switching unit (flow path forming unit) 40 is attached to the center of the lower part of the front surface 30 of the case 10. The switching unit 40 is configured to be able to switch between a state in which the first flow path 51 and the second flow path 52 are connected to the branch flow path 53 (not shown in Figs. 1 and 2) and a state in which the calibration gas flow path (calibration gas inlet path 46 (not shown in Figs. 1 and 2)) is connected to either the first flow path 51 or the second flow path 52 in order to allow calibration gas to flow into each of the first flow path 51 and the second flow path 52. The switching unit 40 has a disk-shaped disk portion 41 and a cylindrical portion 42 that is extended from the disk portion 41 and protrudes forward.

The switching unit 40 has a knurled screw 43 in the center of the disk portion 41, and is fixed to the case 10 by the knurled screw 43. The switching unit 40 is fixed to the case 10 by this knurled screw 43. When the knurled screw 43 is loosened, the switching unit 40 can be moved a predetermined distance away from the case 10 with the knurled screw 43 inserted, and the switching unit 40 can be rotated left and right.

The switching unit 40 will be described with reference to Figures 3 and 4. The disk portion 41 of the switching unit 40 has a first disk portion 61 in which a cylindrical portion 42 is formed, and a second disk portion 62 fixed to the back surface of the first disk portion 61. Below the through hole into which the knurled screw 43 of the first disk portion 61 is inserted, a calibration gas inlet 45 opens at the tip of a calibration gas protrusion 44 that protrudes toward the front side. The calibration gas inlet 45 communicates with a calibration gas inlet passage 46 that penetrates the entire first disk portion 61 and the second disk portion 62.

The mounting portion 32 to which the switching portion 40 of the front surface 30 of the case 10 is attached has a number of openings 33a-33f and a screw hole 34 into which a knurled screw 43 is inserted and screwed. The openings 33a-33f are located on concentric circles centered on the screw hole 34, and are arranged so that adjacent openings are at an angle of 60 degrees. Of the openings 33a-33f, the opening 33c is connected to a common flow path 50 (not shown in Figures 3 and 4) from the gas inlet 12, and the openings 33a and 33b are connected to a first flow path 51 (not shown in Figures 3 and 4) and a second flow path 52 (not shown in Figures 3 and 4), respectively. The remaining openings 33d-33f are not connected to any of the flow paths.

On the back side of the second disk portion 62, protrusions 35a to 35f are formed corresponding to these openings 33a to 33f. Although details will be described later, in normal times, each protrusion 35a to 35f is inserted into the corresponding opening 33a to 33f. The switching portion 40 has a branch flow path 53, which includes a branch flow path inlet 54 that opens at the tip of the protrusion 35c and two branch flow path outlets 55a, 55b that open at the tips of the protrusions 35a and 35b. That is, in this embodiment, the switching portion 40 is formed with a branch flow path 53 that is connected on one side to the opening 33c via the protrusion 35c and is connected on the other side to the openings 33a and 33b via the protrusions 35a and 35b. In this embodiment, the branch flow path 53 means a flow path from the branch flow path inlet 54 to the two branch flow path outlets 55a and 55b. The branch flow inlet 54 and the two branch flow outlets 55a and 55b are located on a concentric circle centered on the screw hole 47 into which the knurled screw 43 is inserted, and are spaced 120 degrees apart from each other. The protrusions 35e and 35f are sealed.

The second disk portion 62 has a common opening 621 formed to face the branch flow inlet 54, and branch openings 622a and 622b formed to face the branch flow outlets 55a and 55b. In addition, a recess 620 is formed in the second disk portion 62 to form the main flow path of the branch flow path 53. The common opening 621 and the branch openings 622a and 622b open on the bottom surface of the recess 620. That is, the recess 620 is shaped so that the flow path from one common opening 621 branches to have the branch opening 622a or the branch opening 622b. In addition, a partition wall 623 is formed on the back side of the first disk portion 61 in correspondence with the recess 620, and the first disk portion 61 and the second disk portion 62 are fixed together to form the branch flow path 53 by the partition wall 623 and the recess 620.

The second disk portion 62 is also formed with a calibration gas recess 624 below the screw hole 47 to form the calibration gas inlet passage 46. The first disk portion 61 is also formed with a calibration gas partition 625 corresponding to the calibration gas recess 624 to form the calibration gas inlet passage 46. When the first disk portion 61 and the second disk portion 62 are fixed together, the calibration gas partition 625 and the calibration gas recess 624 form the calibration gas inlet passage 46. As described above, the calibration gas inlet passage 46 passes through the first disk portion 61 and the second disk portion 62 and communicates with the calibration gas opening 56 that opens at the tip of the first protruding portion 35d.

The entire flow path of the gas detector 1 having such a switching unit 40 will be further described using the schematic diagram shown in FIG. 6. As shown in FIG. 6, a common flow path 50 communicating with the gas inlet 12 and the opening 33c is formed in the case 10. A first flow path 51 and a second flow path 52 are also provided in the case 10. The flow path 51 communicates with the opening 33a, and the flow path 52 communicates with the opening 33b. In FIG. 6, the openings 33a, 33b, and 33c connected to the flow paths are shown as white circles (○), and the openings 33d, 33e, and 33f not connected to the flow paths are shown as black circles (●). A branch flow path 53 is formed in the switching unit 40, and the branch flow path inlet 54 of the protruding portion 35c is connected to the common flow path 50 via the opening 33c, and the branch flow path outlets 55a and 55b of the protruding portions 35a and 35c are connected to the first flow path 51 and the second flow path 52 via the openings 33a and 33b, respectively. In this case, the protrusion 35d of the calibration gas inlet 46 is connected to an opening 33d that is not connected to any flow path.

The first flow path 51 and the second flow path 52 each have two sensors 71-74 for detecting gas, and flow sensors 75a, 75b for detecting the gas flow rate in the flow path. In addition, a capillary 76a (flow rate adjustment unit) is provided between the branching part of the branch flow path 53 and the branch flow path outlet 55a, and a capillary 76b (flow rate adjustment unit) is also provided downstream of the flow sensor 75b in the second flow path.

In this embodiment, the sensors 71 to 74 are provided to detect different gas types, but they may detect the same gas type. In this embodiment, two sensors (sensors 71, 72 and sensors 73, 74) are provided for the first flow path 51 and the second flow path 52, but one may be provided for each flow path. Downstream of the flow sensors 75a, 75b, the first flow path 51 and the second flow path 52 merge again and communicate with the discharge-side common flow path 53. A pump 77 is provided in the discharge-side common flow path 53.

During normal operation of such a gas detector 1, gas introduced from the gas inlet 12 is sucked by the pump 77 while its flow rate is controlled by the capillary 76, passes through the common flow path 50 in the case 10, flows into the branch flow path 53 in the switching unit 40 through the opening 33c, and flows from the branch flow path outlets 55a, 55b through the openings 33a, 33b into the first flow path 51 and the second flow path 52. The gas that has flowed into the first flow path 51 and the second flow path 52 is discharged from the exhaust port 13 via the exhaust common flow path 53. If the gas in the first flow path 51 and the second flow path 52 contains a predetermined gas component, it is detected by the sensors 71 to 74.

The gas calibration operation of the gas detector 1 having such a switching unit 40 will be further explained using the schematic diagram shown in FIG. 7. When introducing a calibration gas, first, the knurled screw 43 is loosened, and the cylindrical part 42 is grasped with the knurled screw 43 inserted into the screw hole to separate the switching unit 40 from the case 10 by a predetermined amount. As a result, the protrusion 35 of the second disk part 62 of the switching unit 40 is pulled out from the opening 33. In this state, the switching unit 40 is rotated 60° to the right and the knurled screw 43 is tightened again, so that the protrusion 35d in which the calibration gas inlet 46 is formed is inserted and fixed in the opening 33a. As a result, the first flow path 51 is connected to the calibration gas inlet 45 as shown in FIG. 7. On the other hand, as the switching unit 40 rotates, the branch flow inlet 54 connected to the common flow path 50 is connected to the opening 33f, and the branch flow outlets 55a and 55b are connected to the openings 33e and 33f, respectively. As a result, the calibration gas flowing in from the calibration gas inlet 45 is introduced into the first flow path 51, making it possible to perform gas calibration only on the sensors 71 and 72 in the first flow path 51.

On the other hand, as shown in FIG. 8, when the protrusion 35d on which the calibration gas inlet 45 is formed is inserted into the opening 33b by rotating the switching unit 40 60° to the left, the second flow path 52 is connected to the calibration gas inlet 46 as shown in FIG. 8. In this case, the gas calibrated from the calibration gas inlet 45 is introduced only into the second flow path 52 from the calibration gas inlet 46, and only the sensors 73 and 74 of the second flow path 52 can perform gas calibration.

In this manner, the gas detector 1 is configured to include a switching unit 40 in the middle of the flow path, so in this embodiment, even if the gas detector has multiple flow paths branching off from a common gas inlet, it is possible to easily perform gas calibration of the sensor for each flow path. In this case, the common flow path 50 and the branch flow paths 53 can also be sealed by rotating the switching unit 40, so it is also possible to prevent gas from mixing into the first flow path 51 or the second flow path 52. In this case, the flow paths can be switched by rotating the switching unit 40, which is preferable because the flow paths can be easily switched with a simple configuration.

However, in such a gas detector 1, when the switching unit 40 rotates, it is possible that the rotation may stop at a position where each protrusion 35 is incompletely inserted into each opening 33 of the case 10, resulting in a gas leak at the joint of the flow path in the switching unit 40.

In order to prevent such gas leakage, in this embodiment, as shown in FIG. 9, signs (sign portions) 38 indicating the positions of the calibration gas protrusion 44 during gas calibration and normal operation are formed around the mounting portion 32 of the case 10. There are three signs 38: 38d indicating the normal position, 38a indicating the position when the first flow path 51 is selected during gas calibration, and 38b indicating the position when the first flow path 51 is selected during gas calibration, and all of them protrude from the case 10. These signs 38 allow visual confirmation of how far the switching portion 40 should be rotated when switching between operations, making it easy to prevent gas leakage.

In addition, it is possible that gas leaks may occur if the knurled screw 43 is not tightened properly after the switching unit 40 is switched, or if normal operation is attempted with the switching unit 40 set to the gas calibration operation position. In order to prevent such gas leakage, in this embodiment, as shown in FIG. 2, a fitting portion 22 that fits into the calibration gas protrusion 44 is formed on the cover 20 side, and if normal operation is attempted with the switching unit 40 set to the gas calibration operation position and the cover 20 is closed, the calibration gas protrusion 44 cannot fit into the fitting portion 22 and comes into contact with it, so that the cover 20 cannot be closed. Specifically, the fitting portion 22 is made of a pair of wall portions 22a, 22b that protrude from the back surface of the cover 20 toward the back side. One end portion 23a, 23b of the pair of wall portions 22a, 22b is spaced apart at a distance that is approximately the same as the outer diameter of the calibration gas protrusion 44. If the calibration gas protrusion 44 is in the correct position when the cover 20 is closed, the calibration gas protrusion 44 is disposed at the spaced apart position of the ends 23a, 23b and engages with the fitting portion 22. In this manner, in this embodiment, if the calibration gas protrusion 44 is not in the correct position, it cannot engage with the fitting portion 22 and the cover 20 cannot be closed, so that a warning can be issued to the user. This makes it possible to prevent gas leakage at the joint of the flow path in the switching portion 40.

Furthermore, in this embodiment, the other ends 24a, 24b of the pair of wall portions 22a, 22b are spaced apart at a distance that is approximately the same as the outer diameter of the knurled screw 43. If the knurled screw 43 is in the correct position when the cover 20 is closed, the knurled screw 43 is arranged at the spaced apart position of the other ends 24a, 24b and fits into the fitting portion 22. In this way, in this embodiment, the fitting portion 22 fits not only with the calibration gas protrusion 44 but also with the knurled screw 43, so that the cover 20 cannot be closed even if the knurled screw 43 is not tightened properly, and the user can be alerted. This makes it possible to further prevent gas leakage at the joint of the switching portion 40. The shape of the fitting portion 22 is not particularly limited as long as it fits into the calibration gas protrusion 44 and/or the knurled screw 43 when the cover 20 is closed. The pair of walls 22a, 22b may not be provided so that one end 23a, 23b and the other end 24a, 24b engage with the calibration gas protrusion 44 and/or the knurled screw 43, but may be provided so that they engage with each other individually.

Furthermore, in this embodiment, the gas detector 1 is configured by arranging the capillaries 76a and 76b so that the flow rate balance in the first flow path 51 and the second flow path 52 is lost when gas leakage occurs at the junction of the flow paths in the switching unit 40. In this case, if there is no gas leakage at the junction of the switching unit 40, the same amount of gas will flow through both the first flow path 51 and the second flow path 52 under normal circumstances. On the other hand, if there is a gas leakage at the junction of the switching unit 40, in this embodiment, the capillaries 76a and 76b are provided on one side upstream of the junction and the other side downstream of the junction in each flow path, so that the flow rate balance between the first flow path 51 and the second flow path 52 is lost. When the flow rate balance is lost in this way, it is possible to determine that there is a leak when the difference in the flow rates detected by the two flow sensors 75a and 75b becomes greater than a predetermined value. Even during gas calibration, for example during the gas calibration operation of the first flow path 51, the flow sensor 75b is sealed so the flow rate should be 0. In that case, if the flow rate of the flow sensor 75b becomes greater than 0, an error can be detected as a gas leak at the junction of the flow paths in the switching unit 40.

In this way, by providing a capillary upstream of the junction of the switching unit 40 in one of the multiple flow paths and providing a capillary downstream of the junction of the switching unit 40 in the other flow path, if a leak occurs at the junction, the flow rate balance will be disrupted, making it possible to detect the flow rate difference in the flow paths early and prevent gas leakage early.

The present invention is not limited to the above-mentioned embodiment. For example, in the above-mentioned embodiment, only the first flow path 51 and the second flow path 52 are shown, but the number of flow paths is not limited to this, and three or more flow paths may be included. In addition, the shape of the switching part is disk-shaped, but is not limited to this. For example, it may be configured to have a polygonal shape according to the number of flow paths, and while being fixed to the case 10 with the knurled screw 43 as in the present embodiment, the knurled screw 43 may be loosened and the case 10 and the polygonal switching part may be separated from the case 10 by a predetermined distance, rotated around the knurled screw 43 according to the polygonal shape, and fixed to the case 10 again. That is, even if the switching part 40 is not circular in front view, the switching part 40 can be rotated to change the opening position relative to the case 10 so as to switch the connection between the branch flow path inlet 54 and the branch flow path outlet 55 of the branch flow path 53, and the opening of the calibration gas inlet 46, and the opening 33 of the first flow path 51 and the second flow path 52, thereby obtaining the same effect as the above-mentioned embodiment.

In the above-described embodiment, a capillary is provided as the flow rate adjustment unit, but the flow rate adjustment unit is not limited to a capillary, and any known flow rate regulator (such as a valve) can be used.

In the above embodiment, the calibration gas was introduced into each flow path for gas calibration, but when performing gas calibration with the same gas for all sensors at the same time, it is also possible to set the switching unit 40 in the same position as during normal operation and introduce the calibration gas from the gas inlet 12 so that the calibration gas is introduced into the first flow path 51 and the second flow path 52.

The above-described embodiments and modifications are described to facilitate understanding of the present invention, and are not described to limit the present invention. Therefore, each element disclosed in the above embodiments and modifications is intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

1 Gas detector 10 Case 11 Bottom surface 12 Gas inlet 13 Gas outlet 13 Outlet 14 Rotating shaft 20 Cover 22 Fitting portion 30 Front surface 31 Display portion 33 Opening 34 Screw hole 35 Protrusion 38 Sign 40 Switching portion 41 Disk portion 42 Cylindrical portion 43 Knurled screw 44 Calibration gas protrusion 45 Calibration gas inlet 46 Calibration gas inlet 47 Screw hole 50 Common flow path 51 First flow path 52 Second flow path 53 Branch flow path 53 Discharge side common flow path 54 Branch flow path inlet 55 Branch flow path outlet 61 First disk portion 62 Second disk portion 71 to 74 Sensor 75 Flow sensor 76 Pump 77 Capillary

Claims (5)

A plurality of flow paths each having one or more sensors disposed therebetween;
a branch flow path connected at one end to one gas inlet and branched into two or more at the other end;
a calibration gas flow path into which a calibration gas flows;
A gas detection device comprising a flow path forming section in which the branch flow path and the calibration gas flow path are formed,
The flow path forming portion is
the flow path forming unit is configured to be switchable between a state in which the plurality of flow paths are connected to the branch flow path and a state in which the calibration gas flow path is connected to one of the plurality of flow paths ,
The gas detector comprises a case;
The case has the plurality of flow paths therein,
an opening of the branch flow path and an opening of the calibration gas flow path are formed on a joint surface of the flow path forming portion and the case,
The case has a joint surface with the flow path forming portion, and openings of the plurality of flow paths are formed in the joint surface,
a flow path forming portion configured to change an opening position of the flow path forming portion so as to switch the connection between the opening of the branch flow path and the opening of the calibration gas flow path and the opening of the multiple flow paths . Among the plurality of flow paths,
A flow rate adjusting unit is provided in one of the flow paths,
2. The gas detector according to claim 1 , wherein the other flow path is provided with another flow rate adjusting section downstream of a branch point of the branch flow path corresponding to the other flow path. a calibration gas protrusion having a calibration gas inlet communicating with the calibration gas flow path formed therein;
The gas detector has a cover that covers at least the calibration gas protrusion,
3. The gas detector according to claim 1, wherein an engagement portion is formed on the inside of said cover, which is adapted to engage with said calibration gas projection when said cover is closed. 4. The gas detector according to claim 3 , further comprising a sign portion for indicating the position of said calibration gas protrusion during normal operation and during calibration operation. The gas detector according to any one of claims 1 to 4, characterized in that the flow path forming portion is made of a disk-shaped disk portion, and the connection state is switched by rotating the disk portion on its center to change the position of the opening.

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