JP5302777B2 - Exhaust gas analyzer and probe unit - Google Patents

Description

  The present invention relates to an exhaust gas analyzer that is attached to an exhaust pipe of a combustion apparatus such as an engine, a boiler, a waste combustion furnace, an industrial furnace, etc., and analyzes a predetermined component contained in an exhaust gas flowing through a flue in the exhaust pipe, and The present invention relates to a probe unit used for this.

  Conventionally, as an exhaust gas analyzer for detecting and analyzing predetermined components such as oxygen or nitrogen oxides contained in exhaust gas in a flue, as shown in Patent Document 1 or Patent Document 2, a probe unit is directly inserted into the flue The exhaust gas is sampled by the probe unit, and a predetermined component such as oxygen or nitrogen oxide in the exhaust gas is detected.

  Specifically, the probe unit includes a gas sensor having a plurality of gas introduction ports for introducing gas into the interior, and the exhaust gas flowing in the flue that is provided in the flue while holding the gas sensor inside the flue. And a sensor holder that leads to the gas sensor.

  In the probe unit of Patent Document 1, the cooling air supplied from the air supply pipe into the sensor holder flows through the cooling air flow path toward the base end of the gas sensor, and smoke passes through the air outlet hole. It is configured to be discharged outside the road, that is, around the exhaust pipe. Note that a lead wire for extracting a detection signal to the outside is connected to the base end portion of the gas sensor by soldering, for example, and cooling air is applied to the base end portion of the gas sensor because of noise contained in the detection signal. This is to make as small as possible.

  However, in the configuration in which the cooling air is discharged outside the flue in this way, the cooling air that has passed through the cooling air flow path and is heated to a high temperature (for example, about 400 ° C.) is discharged to the outside. Not only is there a problem in terms of worker safety, but there are concerns about the thermal effects on peripheral equipment.

  Further, the probe unit of Patent Document 2 is configured such that the cooling air blown to the base end of the gas sensor is discharged into the flue through a communication hole provided in the side wall of the sensor holder.

  However, when the pressure inside the flue is pressurized and the air supply source for cooling air stops due to a power failure or the like, the high-temperature exhaust gas in the flue passes through the communication hole provided in the side wall of the sensor holder. Will flow into the sensor holder. If it does so, high temperature exhaust gas will hit a gas sensor and the thermal influence on a gas sensor will be a problem. In particular, when high-temperature exhaust gas hits a connection portion with a lead wire at the base end portion of the gas sensor, there is a problem that not only the connection portion is deteriorated or damaged, but also noise of a detection signal is increased. In addition, there is a problem that dust in the exhaust gas enters the sensor holder and the inside of the sensor holder becomes dirty, and the cleaning work is complicated, and a lot of work time is required.

JP 2006-184266 A JP 2009-42165 A

  Therefore, the present invention was made to solve the above problems all at once, ensuring the safety of workers and eliminating the thermal effects on peripheral devices, and eliminating the problems caused by the pressure effects in the flue. Doing it is the main desired task.

That is, the probe unit according to the present invention is a probe unit that samples the exhaust gas flowing through the flue in the exhaust pipe , holds the gas sensor inside, and projects the exhaust gas flowing through the flue provided in a protruding manner in the flue. A sensor holder that is provided on the sensor holder, supplies cooling air to the gas sensor and has a cooling air discharge port, and one end connected to the cooling air exhaust port. A discharge pipe whose other end communicates with the inside of the flue, and a check valve provided on the discharge pipe and allowing only the flow from the cooling air discharge side to the flue side, and the sensor holder The cooling air discharge port is attached to the flange portion fixed to the exhaust pipe, and the cooling air discharge port is provided on the opposite side of the flue to the flange portion. Characterized in that it is connected to a through hole formed in the flange portion.

  If this is the case, a discharge pipe is connected to the cooling air discharge port, and this discharge pipe communicates with the inside of the flue, so that the heated cooling air is not discharged outside the flue. The safety of the person can be ensured, and the thermal influence on the peripheral equipment can be eliminated. In addition, since a check valve is provided in the discharge pipe, it is possible to prevent the exhaust gas in the flue from flowing into the cooling air flow path when the pressure in the flue is pressurized. Can solve the problem.

  The sensor holder has a double tube structure consisting of an inner tube and an outer tube, the gas sensor is held in the inner tube, and an outward path in the cooling air flow path is formed in the inner tube, A return path in the cooling air flow path is formed in a space formed by the inner pipe and the outer pipe, and a communication hole that communicates the forward path and the return path is formed on the axial front end side of the inner pipe. desirable. In this case, since the communication hole is formed on the tip end side in the axial direction, the cooling air hits the entire accommodating portion in the inner pipe of the gas sensor, so that the gas sensor can be sufficiently cooled. In addition, when the cooling air flows through the air between the inner pipe and the outer pipe, a heat insulating effect is exerted with the exhaust gas in the flue, and the gas sensor can be further cooled.

  Further, an exhaust gas analyzer according to the present invention uses the above probe unit, and holds a gas sensor inside, and is a sensor holder that protrudes into the flue and guides the exhaust gas flowing through the flue to the gas sensor. A cooling air flow path provided in the sensor holder to supply cooling air to the gas sensor, a cooling air discharge port provided outside the flue, and one end connected to the cooling air exhaust port, A discharge pipe having the other end communicating with the inside of the flue, and a check valve provided on the discharge pipe and allowing only the flow from the cooling air discharge port side to the flue side are provided.

  According to the present invention configured as described above, it is possible to ensure the safety of the worker, eliminate the thermal influence on the peripheral devices, and eliminate the problems due to the pressure influence in the flue.

In the exhaust gas analyzer according to one embodiment of the present invention, it is a schematic diagram mainly showing a calibration gas channel and a cleaning / measurement gas channel. In the exhaust gas analyzer of the same embodiment, it is a schematic diagram mainly showing a cooling air flow path. It is sectional drawing along the axial direction which shows the front-end | tip part of the probe unit of the embodiment. It is an exploded sectional view of the probe unit of the embodiment.

  Hereinafter, an embodiment of an exhaust gas analyzer according to the present invention will be described with reference to the drawings.

<Device configuration>
The exhaust gas analyzer 100 according to the present embodiment is used for exhaust gas G flowing through a flue in an exhaust pipe H connected to a boiler such as a coal fired boiler or a heavy oil fired boiler, or an internal combustion engine such as a gas engine or a marine engine. This is a direct insertion type exhaust gas analyzer that analyzes predetermined components (for example, NO _X , SO _X , CO ₂ , CO, etc.). The analysis result (for example, the concentration of the predetermined component) obtained by the exhaust gas analyzer 100 is used for control of denitration or desulfurization.

  Specifically, as shown in FIG. 1 and FIG. 2, this has a gas sensor 4 that is fixed to the exhaust pipe H so that its tip protrudes into the flue and detects a predetermined component inside. A probe unit 2 and a control unit 3 that receives a detection signal from the probe unit 2, receives the detection signal, and analyzes a predetermined component contained in the exhaust gas G continuously and with a high-speed response. The control unit 3 includes an arithmetic processing unit, a display unit, and the like (not shown), and the probe unit 2 and the control unit 3 are connected by a cable.

  As shown in FIGS. 1 and 2, the probe unit 2 samples the exhaust gas G flowing through the flue and detects a predetermined component contained in the sampled exhaust gas G. As shown in FIG. A gas sensor 4 having a plurality of gas introduction holes 4a for introducing gas into the inside, and a sensor holder 5 that holds the gas sensor 4 inside and projects the exhaust gas G flowing through the flue to the gas sensor 4 so as to protrude into the flue. And.

  The gas sensor 4 includes a sensor element of a high temperature operation type using a plate-like or rod-like oxygen ion conductive solid electrolyte, a heater for heating the sensor element, and a sensor case having a substantially cylindrical shape that houses the sensor element and the heater. And. As shown in FIG. 3, a plurality of gas introduction holes 4a for guiding gas to the sensor element are formed at a predetermined interval in the circumferential direction of the sensor case (this embodiment). In the form, it is equally distributed by 90 degrees. In addition, the sensor element is provided with a pair of electrodes, and is configured to be able to detect the concentration of a predetermined component in the exhaust gas G by measuring a current generated due to a potential difference between the two electrodes. A lead wire C for outputting the current generated by the sensor element to the outside is connected to the base end portion of the sensor case by, for example, soldering (see FIG. 3).

  The sensor holder 5 has a substantially cylindrical shape, and is configured so that the outer diameter of at least the outer peripheral surface of the portion inserted into the exhaust pipe H is constant. Further, a flange portion 501 is formed at the base end portion of the sensor holder 5 to be screwed to a mounting portion H1 provided on the exhaust pipe H (see FIG. 1 and the like). As shown in FIG. 3, an opening 502 for introducing the exhaust gas G into the sensor holder 5 is formed at the tip of the sensor holder 5. Further, the opening 502 is provided with a dustproof filter F for removing dust in the exhaust gas G sampled in the sensor holder 5. Reference numeral 6 in FIG. 3 is a surrounding plate that extends from the tip of the sensor holder 5 and that surrounds the opening 502 and the space in front of the filter F at least from the upstream side of the flue.

  In order to increase the surface area as much as possible, the filter F has a substantially bottomed cylindrical shape, and is attached so as to cover the opening 502 of the sensor holder 5 so that the bottom wall is on the tip side. With this configuration, it is possible to increase the surface area of the filter F as much as possible and prevent the exhaust gas G from being blocked due to the filter F being clogged. In addition, the influence of pressure due to clogging of the filter F during calibration can be reduced.

  Further, as shown in FIG. 3, the sensor holder 5 includes a double pipe element 51 having a double pipe structure composed of an inner pipe 511 and an outer pipe 512, and the gas sensor 4 disposed inside the distal end side of the double pipe element 51. And a fixing element 52 for receiving and fixing. The proximal end portion of the gas sensor 4 is accommodated in the inner tube 511 of the double tube element 51, and the distal end portion of the gas sensor 4 is accommodated in the fixing element 52. Specifically, the fixing element 52 has a hollow portion 521 that accommodates a tip portion (including a portion where the gas introduction hole 4a is formed) of the gas sensor 4 therein. The opening on the front end side of the hollow portion 521 becomes the opening portion 502 of the sensor holder 5. Further, the inner surface 521a of the hollow portion 521 is formed concentrically with the outer peripheral surface in which the gas introduction hole 4a in the gas sensor 4 is formed.

<Regarding calibration gas flow path L1>
Then, as shown in FIG. 3, the sensor holder 5 of the present embodiment opens on the inner surface of the side wall surrounding the gas introduction hole 4 a of the gas sensor 4, that is, the inner surface 521 a of the hollow portion 521, and supplies the calibration gas to the gas sensor 4. A calibration gas flow path L1 is formed.

  The calibration gas flow path L1 is connected between the inner pipe 511 and the outer pipe 512 of the sensor holder 5 along the axial direction of the sensor holder 5 and the calibration gas pipe 7 connected to the calibration gas pipe 7. The internal flow path 51 a is formed in the distal end wall of the heavy pipe element 51, and the internal flow path 52 a is formed in the fixing element 52 of the sensor holder 5. A calibration gas supply source (not shown) is connected to an external connection port (not shown) of the calibration gas pipe 7. A connection pipe 522 for welding to the internal flow path 51 a on the distal end wall of the double pipe element 51 is welded to the opening on the pipe connection side of the internal flow path 52 a of the fixing element 52. The connecting pipe 522 is fitted into the internal flow path 51a of the double pipe element 51, whereby the calibration gas flow path L1 is formed.

  In the calibration gas flow path L1 configured in this way, the downstream opening side of the calibration gas flow path L1 narrows the flow path to increase the flow rate of the calibration gas, and the gas sensor 4 (specifically, the gas introduction hole 4a). It is comprised so that it may be supplied to. Specifically, by making the inner diameter of the internal flow path 52a formed in the fixing element 52 smaller than the inner diameter (for example, 6 mm) of the calibration gas pipe 7 (for example, 4 mm), the downstream opening in the calibration gas flow path L1. The flow path on the side is narrowed.

<About guide groove 8>
Therefore, as shown in FIG. 3, the sensor holder 5 of the probe unit 2 of the present embodiment is continuously provided in the downstream opening of the calibration gas flow path L1, and a plurality of calibration gases from the calibration gas flow path L1 are supplied. A guide groove 8 is provided to reach the gas introduction hole 4a.

  The guide groove 8 is provided along the arrangement direction so as to face the plurality of gas introduction holes 4a on the inner surface 521a of the hollow portion 521. Since the gas introduction hole 4a of the present embodiment is provided along the circumferential direction of the gas sensor 4 (specifically, a cylindrical sensor case), the guide groove 8 is also provided along the circumferential direction. Further, the guide groove 8 is formed over the entire circumference of the inner surface 521a of the hollow portion 521 so that the calibration gas emitted from the calibration gas flow path L1 can be distributed evenly in the circumferential direction. In FIG. 2 and the like, the guide groove 8 has a V-shaped cross section, but any other calibration gas may be used as long as the calibration gas flowing along the guide groove 8 flows toward the gas introduction hole 4a. A concave shape or a semicircular cross section may be used.

  By providing the guide groove 8 in this way, on the inner surface 521a of the hollow portion 521 surrounding the gas introduction hole 4a, the guide groove 8 is provided along the arrangement direction of the plurality of gas introduction holes 4a. The calibration gas supplied from the calibration gas flow path L1 flows along the guide groove 8 and can be made less susceptible to the pressure effect in the flue, particularly the influence of the suction pressure, and the consumption of the calibration gas is increased. The calibration gas can be spread over all of the plurality of gas introduction holes 4a without causing them. Further, since the guide groove 8 continuous to the opening of the calibration gas flow path L1 is provided along the arrangement direction of the plurality of gas introduction holes 4a, the positional relationship between the opening of the calibration gas flow path L1 and the gas introduction holes 4a. Regardless of whether the calibration gas can be guided to the gas introduction hole 4a, the gas sensor 4 can be easily mounted in the sensor holder 5.

<About the cooling air flow path L2>
Further, as shown in FIG. 2, the sensor holder 5 is supplied with cooling air to the gas sensor 4 and has a cooling air flow path L2 provided with a cooling air discharge port P1 outside the flue, and one end of the cooling air. A discharge pipe 9 connected to the exhaust port P1 and having the other end communicating with the inside of the flue, and a check valve 10 provided on the discharge pipe 9 and allowing only the flow from the cooling air discharge port side to the flue side. And are provided.

  As shown in FIG. 3, the cooling air flow path L <b> 2 is a cooling air formed in a space formed by the cooling air forward path L <b> 21 formed in the inner pipe 511 and the inner pipe 511 and the outer pipe 512. It consists of a return path L22. In this embodiment, the space itself in the inner pipe 511 forms the cooling air forward path L21, and the space itself between the inner pipe 511 and the outer pipe 512 forms the cooling air return path L22. The cooling air forward path L21 and the cooling air return path L22 are communicated with each other through one or a plurality of communication holes 511h formed on the distal end side in the axial direction of the inner pipe 511.

  A cooling air supply source (not shown) for introducing cooling air into the inner pipe 511 is connected to the axially proximal end side of the inner pipe 511. Further, the downstream opening (cooling air discharge port P1) of the cooling air forward path L22 is provided outside the flue by being provided on the axially proximal end side of the outer pipe 512.

  Thus, since the entire space in the inner pipe 511 becomes the cooling air forward path L21, the cooling air can be uniformly applied to the entire base end portion of the gas sensor 4 accommodated in the inner pipe 511. The base end portion of 4 can be efficiently cooled. In addition, when the cooling air flows through the air between the inner pipe 511 and the outer pipe 512, a heat insulating effect is exhibited with the exhaust gas G in the flue, and the gas sensor 4 can be further cooled.

  The other end of the discharge pipe 9 is connected to a through hole 501 h formed in the flange portion 501. The through hole 501h is formed on the flange portion 501 on the downstream side of the flue. And in the state which fixed the flange part 501 of the sensor holder 5 to the attachment part H1 of the exhaust pipe H, the cooling air which passed the through-hole 501h inserted the sensor holder 5 of the outer peripheral surface of the sensor holder 5 and the exhaust pipe H. It passes through the gap S1 formed between the inner surface of the hole and is discharged downstream of the flue with respect to the probe unit 2. Thereby, the cooling air from the cooling air discharge port P1 can be discharged into the flue without performing any processing on the exhaust pipe H constituting the flue. Further, since the cooling air is discharged to the downstream side of the flue, it is possible to prevent an adverse effect on the measurement result caused by discharging the cooling air into the flue. Furthermore, since the check valve 10 is disposed outside the flue, the thermal effect that the check valve receives from the exhaust gas G can be ignored.

<About cleaning / measurement gas flow path L3>
Further, as shown in FIG. 1, the sensor holder 5 supplies cleaning gas for cleaning the filter F, or conducts cleaning / measurement for guiding a part of the exhaust gas G that has passed through the filter F to a measuring device different from the gas sensor 4. A gas flow path L3.

  As shown in FIG. 3, the cleaning / measurement gas flow path L <b> 3 is provided between the inner tube 511 and the outer tube 512 of the sensor holder 5 along the axial direction of the sensor holder 5. , Simply referred to as the cleaning gas pipe 11), the internal flow path 51 b formed in the distal end wall of the double pipe element 51 to which the cleaning gas pipe 11 is connected, and the fixing element 52 of the sensor holder 5. And an internal flow path 52b. As shown in FIG. 3, a measuring device 13 different from the cleaning gas supply source 12 or the gas sensor 4 is connected to the external connection port P <b> 2 provided outside the flue of the cleaning gas pipe 11. A connection pipe 523 is welded to the pipe connection side opening of the internal flow path 52b of the fixing element 52 in the same manner as the calibration gas flow path L1. Then, the connection / pipe 523 is fitted into the internal flow path 51b of the double pipe element 51, thereby forming the cleaning / measurement gas flow path L3. The internal flow path 52b of the fixing element 52 that constitutes the cleaning / measurement gas flow path L3 is configured to open in the guide groove 8, but is not limited thereto, and the opening is avoided by avoiding the guide groove 8. You may make it let it.

  In the cleaning / measurement gas flow path L3 configured in this way, the connection port P2 of the cleaning / measurement gas flow path L3 is connected to the cleaning gas supply source 12 during filter cleaning. The cleaning gas supplied from the cleaning gas supply source 12 is supplied to the hollow portion 521 of the fixing element 52 through the cleaning gas pipe 11 and the internal flow paths 51b and 52b, and is supplied to the hollow portion 521. The cleaning gas flows through the filter F from the gas sensor side to the flue side. By flowing the cleaning gas through the filter F in this way, dust clogged in the filter F is removed to the flue side.

  On the other hand, at the time of measurement (for example, at the time of comparative measurement or at the time of measuring the sensitivity of the gas sensor 4), the connection port P <b> 2 of the cleaning / measurement gas flow path L <b> 3 is connected to the measurement device 13 different from the gas sensor 4. In the measurement, a part of the exhaust gas G that has passed through the filter F is guided to the measuring device 13 through the cleaning gas pipe 11 and the internal flow paths 51b and 52b, and the measuring device 13 measures the exhaust gas G. Here, by changing the type of the measuring device 13 to be connected, comparative measurement for checking the sensitivity deterioration of the gas sensor 4 can be performed, or a measurement item different from the measurement item of the gas sensor 4 can be measured. it can.

  At the time of calibration, a part of the calibration gas supplied to the fixing element 52 is guided to the measuring device 13 through the internal flow paths 51b and 52b and the cleaning gas pipe 11, so that known components of the calibration gas are obtained. By comparing the concentration and the measurement result by the measuring device 13, gas leakage in the sensor holder 5 can be checked. At this time, since the cleaning / measurement gas flow path L3 is continuously open to the guide groove 8, the calibration gas from the calibration gas flow path L1 can be efficiently guided to the cleaning / measurement gas flow path L3.

<Assembly method and seal structure>
Finally, a method for assembling the probe unit 2 will be described with reference to FIG.
First, the filter F is fixed by the fixing tool 15 through the sealing member 14 such as graphite packing in the vicinity of the opening (opening portion 502) of the hollow portion 521 of the fixing element 52. Note that the fixing tool 15 of the present embodiment is a cap type, and fixes the filter F to the fixing element 52 by screwing into a screw portion (not shown) formed in the fixing element 52.

  On the other hand, after a seal member 16 such as graphite packing and a sensor fixing plate 17 are put in this order into a threaded portion 4b formed on the rear side of the gas introduction hole 4a on the outer peripheral surface of the gas sensor 4, a fixing nut 18 is provided. Is screwed into the threaded portion 4b. Then, the seal member 16 and the sensor fixing plate 17 are sandwiched between the fixing nut 18 and the sensor nut 19.

  Thereafter, the base end portion of the gas sensor 4 is inserted into the double pipe element 51, and the fixing element 52 is connected from the distal end side of the gas sensor 4. The connection pipes 522 and 523 of the fixing element 52 are connected to the double pipe element 51. It fits so that it may fit in each internal flow path 51a, 51b. Then, the double pipe element 51 and the fixing element 52 are fastened by a fixing screw (not shown). As a result, the seal member 16 and the sensor fixing plate 17 are sandwiched between the double tube element 51 and the fixing element 52, and the probe unit 2 is assembled. At this time, the seal member 16 attached to the gas sensor 4 is interposed between the double pipe element 51 and the fixing element 52. As a result, the portion where there is a risk of gas leakage is only on the double pipe element 51 side, and even if a gas leak occurs, it is sealed by the seal member 16 between the double pipe element 51 and the fixing element 52. Will be. Accordingly, gas leakage can be prevented with a small number of seal members, and cost reduction, simplification of the structure, and ease of assembly work can be achieved.

  Further, as shown in a partially enlarged view in FIG. 3 and FIG. 4, an accommodation recess 51 x that accommodates at least the seal member 16 is formed on the front surface of the distal end wall of the double pipe element 51. And in the state fastened with the double pipe element 51 and the fixing element 52, the sealing member 16 is accommodated in the accommodating recess 51x and is configured not to directly contact the exhaust gas in the flue. This can prevent the seal member 16 from being eroded by the exhaust gas.

<Effect of this embodiment>
According to the exhaust gas analyzer 100 according to the present embodiment configured as described above, the exhaust pipe 9 is connected to the cooling air discharge port P1, and the exhaust pipe 9 is communicated with the inside of the flue. It is possible to ensure the safety of the worker without discharging the working air outside the flue, and to eliminate the thermal influence on the peripheral equipment. In addition, since the check valve 10 is provided in the discharge pipe 9, it is possible to prevent the exhaust gas in the flue from flowing into the cooling air flow path L2 when the pressure in the flue is pressurized. It is possible to eliminate problems caused by the pressure effect.

<Other modified embodiments>
The present invention is not limited to the above embodiment.

  For example, in the above-described embodiment, the sensor holder 5 has a double tube structure, and the space itself in the inner tube is used as a cooling air forward passage, and the space itself between the inner tube and the outer tube is used as a cooling air return passage. A pipe constituting the cooling air forward path may be provided in the pipe, and a pipe constituting the cooling air return path may be provided between the inner pipe and the outer pipe.

  Moreover, you may provide the piping which comprises the piping which comprises the air path for cooling, and the return path for cooling air, without making a sensor holder into a double pipe structure.

  In addition, the through hole to which the other end of the discharge pipe of the embodiment is connected is formed in the flange portion, but may be formed in the discharge pipe. In this case, it is preferable to be formed on the downstream side of the flue from the probe unit, as in the above embodiment. In addition, if the influence on the measurement of the cooling air discharged into the flue is negligible, that is, if the distance between the opening of the sensor holder and the through hole is sufficient, the through hole should be located upstream of the flue. May be provided.

  In addition, it goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Exhaust gas analyzer 2 ... Probe unit 4 ... Gas sensor 5 ... Sensor holder L2 ... Cooling air flow path P1 ... Cooling air discharge port 9 ... Exhaust pipe 10 ··Check valve

Claims (3)

A probe unit for sampling exhaust gas flowing through a flue in an exhaust pipe ,
A sensor holder for holding a gas sensor inside and projecting into the flue and guiding exhaust gas flowing through the flue to the gas sensor;
A cooling air flow path provided in the sensor holder for supplying cooling air to the gas sensor and provided with a cooling air outlet;
A discharge pipe having one end connected to the cooling air exhaust port and the other end communicating with the flue;
A check valve provided on the discharge pipe and allowing only the flow from the cooling air discharge port side to the flue side ,
The sensor holder is attached to a flange portion fixed to the exhaust pipe,
The cooling air outlet is provided on the opposite side of the flue to the flange portion;
A probe unit in which the other end of the discharge pipe is connected to a through hole formed in the flange portion . The sensor holder has a double tube structure consisting of an inner tube and an outer tube,
While the gas sensor is held in the inner pipe, an outward path in the cooling air flow path is formed in the inner pipe,
A return path in the cooling air flow path is formed in a space formed by the inner pipe and the outer pipe,
The probe unit according to claim 1, wherein a communication hole that communicates the forward path and the return path is formed on an axially distal end side of the inner pipe. An exhaust gas analyzer using the probe unit according to claim 1.