Patent Publication Number: US-2022229032-A1

Title: Exhaust gas analyzing device, gas supply method, and exhaust gas sampling device

Description:
TECHNICAL FIELD 
     The present invention relates to an exhaust gas analyzing device and a gas supply method that supplies gas to the exhaust gas analyzing device. 
     BACKGROUND ART 
     As a conventional exhaust gas analyzing device, as shown in Patent Literature 1, there is an exhaust gas analyzing device including a so-called recirculating dilution mechanism that includes a recirculated channel that returns part of exhaust gas flowing through a sampling channel from downstream to upstream, includes a filter in the recirculated channel, and thus returns the exhaust gas flowing into the recirculated channel to the sampling channel as a dilution gas. 
     In such an exhaust gas analyzing device, a zero level of the analyzer has to be checked and calibrated and the sampling channel has to be purged, for example, before and after exhaust gas analysis in order to ensure analysis accuracy. 
     However, in order to perform calibration and purge, the sampling probe of the sampling channel is removed from the sampling location, a filter is attached to the sampling probe, air or the like is taken in through the filter, and the zero check and purge are performed, which complicates work. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP 2014-526679 A 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     Therefore, the present invention has been made to solve the above problems at once, and a main object of the present invention is to provide an exhaust gas analyzer capable of calibrating an analyzer or purging a sampling channel without removing a sampling probe from a sampling location. 
     Solution to Problem 
     An exhaust gas analyzing device of the present invention includes a sampling channel through which exhaust gas from an internal combustion engine flows, an analyzer that is connected to the sampling channel and analyzes the exhaust gas, a diluter provided upstream of the analyzer in the sampling channel, a recirculated channel that branches from a branch point set between the analyzer and the diluter in the sampling channel and joins the diluter, a pump that is provided in the recirculated channel and guides part of the exhaust gas from the branch point to the diluter, an additional channel that is connected to the recirculated channel or the sampling channel and through which a calibration gas or a purge gas flows, and an opening and closing mechanism provided in the additional channel 
     In the exhaust gas analyzing device configured as described above, the additional channel through which the calibration gas or the purge gas flows is connected to the recirculated channel or the sampling channel, and thus the calibration gas or the purge gas can flow into the recirculated channel or the sampling channel by opening the opening and closing mechanism of the additional channel. As a result, the analyzer can be calibrated or the sampling channel can be purged without removing the sampling probe of the sampling channel from the sampling location. 
     In order to prevent the exhaust gas from flowing into the analyzer at a time of calibration or purge, when the opening and closing mechanism is opened, part of the calibration gas or the purge gas introduced from the additional channel into the recirculated channel preferably flows to upstream of the sampling channel through the diluter. 
     In such a configuration, part of the calibration gas or the purge gas flows backward in the sampling channel through the diluter, it is therefore possible to prevent the exhaust gas from flowing into the analyzer. 
     In order to reliably cause part of the calibration gas or the purge gas to flow backward, an analysis gas flow rate as a flow rate of a gas introduced into the analyzer is preferably controlled to a first flow rate, and an additional flow rate as a flow rate of the calibration gas or the purge gas introduced from the additional channel into the recirculated channel is preferably larger than the first flow rate. 
     Further, a flow rate of a gas flowing from the recirculated channel to the diluter is preferably controlled to a second flow rate, and an additional flow rate as a flow rate of the calibration gas or the purge gas introduced from the additional channel into the recirculated channel is preferably smaller than the second flow rate. 
     A specific embodiment can be exemplified in which the analyzer analyzes a component contained in the exhaust gas in a state where the opening and closing mechanism is closed, and the calibration gas or the purge gas flows through the additional channel in a state where the opening and closing mechanism is opened. 
     A specific device configuration can be exemplified in which the analyzer analyzes a particulate matter in the exhaust gas, and the recirculated channel is provided with a filter that captures the particulate matter. 
     The filter is preferably provided upstream of the pump in the recirculated channel 
     This configuration can reduce a particulate matter flowing into the pump and prevent a failure of the pump. 
     The additional channel is preferably connected between the pump and the filter in the recirculated channel. 
     In such a configuration, at a time of exhaust gas analysis, the dilution gas in which the particulate matter is captured from the exhaust gas flows through a connection of the additional channel, and contamination of the additional channel can be reduced. 
     In a case where atmosphere is used as the calibration gas or the purge gas, the additional channel is preferably provided with a second filter that captures a particulate matter in atmosphere, and the atmosphere having passed through the second filter as the calibration gas or the purge gas is preferably introduced into the recirculated channel from the additional channel in a state where the opening and closing mechanism is opened. 
     It is preferable to further include a dehumidifier provided downstream of the pump in the recirculated channel 
     The calibration gas or the purge gas can be dried and allowed to flow, and this can suppress condensation of moisture contained in these gases. 
     A calibration method of the present invention is a method of supplying a gas to an exhaust gas analyzing device including a sampling channel through which exhaust gas from an internal combustion engine flows, an analyzer that is connected to the sampling channel and analyzes the exhaust gas, a diluter provided upstream of the analyzer in the sampling channel, a recirculated channel that branches from a branch point set downstream of the diluter in the sampling channel and is connected to the diluter, and a pump that is provided in the recirculated channel and guides part of the exhaust gas from the branch point to the diluter, the method including connecting an additional channel through which a calibration gas or a purge gas flows to the recirculated channel or the sampling channel, and guiding the calibration gas or the purge gas to the sampling channel by opening an opening and closing mechanism provided in the additional channel 
     An exhaust gas sampling device of the present invention samples exhaust gas from an internal combustion engine to an analyzer, the exhaust gas sampling device including a sampling channel that is connected to the analyzer and through which the exhaust gas flows, a diluter provided upstream of the analyzer in the sampling channel, a recirculated channel that branches from a branch point set between the analyzer and the diluter in the sampling channel and joins the diluter, a pump that is provided in the recirculated channel and guides part of the exhaust gas from the branch point to the diluter, an additional channel that is connected to the recirculated channel or the sampling channel and through which a calibration gas or a purge gas flows, and an opening and closing mechanism provided in the additional channel. 
     Such a gas supply method and an exhaust gas sampling device make it possible to obtain effects similar to effects of the above exhaust gas analyzing device. 
     Advantageous Effects of Invention 
     The present invention configured as described above allows the analyzer to be calibrated or the sampling channel to be purged without removing the sampling probe from the sampling location. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic diagram illustrating a usage mode of an exhaust gas analyzing device according to an embodiment. 
         FIG. 2  is a schematic diagram illustrating a configuration of the exhaust gas analyzing device according to the embodiment. 
         FIG. 3  is a schematic diagram illustrating a principle of an analyzer according to the embodiment. 
         FIG. 4  is a flowchart for describing an operation of the exhaust gas analyzing device according to the embodiment. 
         FIG. 5  is a schematic diagram for describing a gas flow rate flowing through the exhaust gas analyzing device according to the embodiment. 
         FIG. 6  is a schematic diagram illustrating a configuration of an exhaust gas analyzing device according to another embodiment. 
         FIG. 7  is a schematic diagram illustrating a configuration of an exhaust gas analyzing device according to another embodiment. 
         FIG. 8  is a schematic diagram illustrating a configuration of an exhaust gas analyzing device according to another embodiment. 
         FIG. 9  is a schematic diagram illustrating a configuration of an exhaust gas analyzing device according to another embodiment. 
     
    
    
     REFERENCE SIGNS LIST 
       100  exhaust gas analyzing device 
       1  exhaust gas sampling device 
     L 1  sampling channel 
     L 2  recirculated channel 
     X analyzer 
       10  dilution mechanism 
     MIX diluter 
     P pump 
     F 1  first filter 
       11  flow rate controller 
     L 3  additional channel 
     V 1  opening and closing mechanism 
       20  control device 
     Description of Embodiments 
     Hereinafter, an embodiment of an exhaust gas analyzing device of the present invention will be described with reference to the drawings. 
     As shown in  FIG. 1 , an exhaust gas analyzing device  100  according to the embodiment is an in-vehicle device mounted in a vehicle VH. However, the exhaust gas analyzing device  100  may be a stationary device that is not mounted in the vehicle VH. 
     Specifically, as illustrated in  FIG. 2 , the exhaust gas analyzing device  100  includes an exhaust gas sampling device  1  that samples exhaust gas discharged from an internal combustion engine E, and an analyzer X that analyzes the sampled exhaust gas. 
     The exhaust gas sampling device L 1  includes an exhaust gas sampling channel L 1  provided with a sampling probe (not illustrated) at one end, and samples part or all of the exhaust gas discharged from the internal combustion engine E by attaching the sampling probe to, for example, a sampling location near a tail pipe. Here, the sampling channel L 1  is constituted partially by a heating tube unit called a hot hose, and guides the collected exhaust gas to the analyzer X while heating the exhaust gas to a predetermined temperature or maintaining the exhaust gas at a predetermined temperature. 
     The analyzer X is connected to the other end of the sampling channel L 1  and analyzes a particulate matter contained in the exhaust gas. The analyzer X is here a particle number counting mechanism X that counts the number of particles (PN) of the particulate matter. 
     Examples of the particle number counting mechanism include a mechanism called a condensation particle counter (CPC) as illustrated in  FIG. 3 . The CPC guides exhaust gas to a heater A  1  including an organic gas such as alcohol or butanol, and then cools the exhaust gas in a condenser A 2  to condense and adhere the organic gas to a particulate matter in the exhaust gas and grow the particulate matter to have a large diameter, discharges the grown particulate matter from a slit A 3 , and counts discharged particles with a laser light R. Downstream of the CPC, a critical-orifice constant flow rate unit (not shown) is provided as a flow rate controller, and a constant flow rate of gas flows through the CPC. 
     In a case where the particle number counting mechanism X is used, the exhaust gas has to be guided to the particle number counting mechanism after being diluted in order to prevent the particulate matter contained in the exhaust gas from aggregating with each other. In the analyzer X analyzing a component different from the particulate matter contained in the exhaust gas, the exhaust gas has to be diluted for various reasons in some cases. 
     Therefore, as shown in  FIG. 2 , the exhaust gas sampling device  1  according to the embodiment further includes a dilution mechanism  10  that dilutes sampled exhaust gas. 
     The dilution mechanism  10  is a so-called recirculating mechanism that samples part of the exhaust gas flowing through the sampling channel L 1 , removes a particulate matter (counting target) contained in the exhaust gas to obtain a dilution gas, and then returns the dilution gas to the sampling channel L 1 . 
     Specifically, the dilution mechanism  10  includes a recirculated channel L 2  that branches from a branch point L 1  a set on the sampling channel L 1 , joins a junction Llb set on the sampling channel L 1 , and returns part of the exhaust gas flowing through the sampling channel L 1  from downstream to upstream of the sampling channel L 1 . In the embodiment, a diluter MIX is provided at the junction Llb, and a branch point L 1   a  is set between the diluter MIX and the analyzer X. 
     The recirculated channel L 2  is provided with a pump P that circulates a fluid flowing through the recirculated channel L 2 . A first filter F 1  that captures the particulate matter contained in the exhaust gas may be provided upstream of the pump P, that is, between the pump P and the branch point Ll a in order to prevent a failure or the like of the pump P. 
     A flow rate controller  11  that controls a dilution gas flow rate as a flow rate of the dilution gas flowing into the diluter MIX from the recirculated channel L 2  is provided downstream of the pump P in the recirculated channel L 2 , that is, between the pump P and the diluter MIX. Here, the flow rate controller  11  is a venturi as a constant flow rate unit, but for example, a mass flow controller, a flow rate adjusting valve, or the like may be used. 
     Furthermore, in order to prevent a particulate matter such as pump dust from being contained in the dilution gas flowing into the diluter MIX, a second filter F 2  that captures the particulate matter may be provided downstream of the pump P in the recirculated channel L 2 , that is, between the pump P and the diluter MIX. Here, the second filter F 2  is provided between the pump P and the flow rate controller  11 , but may be provided between the flow rate adjuster  11  and the diluter MIX. 
     In addition, a dehumidifier  12  that reduces humidity of the dilution gas flowing into the diluter MIX may be provided downstream of the pump P in the recirculated channel L 2 , that is, between the pump P and the diluter MIX. Here, the dehumidifier  12  is provided between the pump P and the second filter F 2 , but may be provided between the second filter F 2  and the flow rate controller  11 , between the flow rate controller  11  and the diluter MIX, or upstream of the pump P. 
     The exhaust gas analyzing device according to the embodiment further includes an additional channel L 3  connected to upstream of the pump P in the recirculated channel L 2  and through which a calibration gas or a purge gas flows, and an opening and closing mechanism V 1  provided in the additional channel L 3 . In the embodiment, the exhaust gas analyzing device  100  further includes a control device  20  that controls the opening and closing mechanism V 1  to be in an open state or a closed state. When the opening and closing mechanism V 1  is manually opened and closed, a function related to the control device  20  described later need not be used. 
     The additional channel L 3  has one end into which the calibration gas or the purge gas is introduced, and the other end connected to upstream (negative pressure side) of the pump P in the recirculated channel L 2 . The calibration gas is a zero gas for zero check of the analyzer X, and in other words, a gas substantially not containing a particulate matter. In this embodiment, the calibration gas is also used as the purge gas. 
     In this embodiment, air (atmosphere) is used as the calibration gas or the purge gas, and the third filter F 3  for capturing a particulate matter contained in the air is provided in the additional channel L 3 . Here, the third filter F 3  is provided upstream of the opening and closing mechanism V 1 , but may be provided downstream of the opening and closing mechanism V 1 . 
     The additional channel L 3  is provided with a flow rate adjusting valve V 2  which is a flow rate controller that adjusts an additional flow rate as a flow rate of the calibration gas or the purge gas, and the flow rate of the calibration gas or the purge gas supplied from the additional channel L 3  to the recirculated channel L 2  becomes a constant flow rate. As the flow rate controller, a mass flow controller, a plurality of venturi connected in parallel to be switchable, or the like may be used. 
     The opening and closing mechanism V 1  is switchable between an open state in which the calibration gas or the purge gas is supplied from the additional channel L 3  to the recirculated channel L 2  and a closed state in which the supply of the calibration gas or the purge gas is stopped. Here, the opening and closing mechanism V 1  is an opening and closing valve such as an electromagnetic valve operated according to a control signal from the control device  20 . 
     The control device  20  physically includes a CPU, an internal memory, an input and output interface, and the like, receives an analysis start signal, a calibration start signal, and a purge start signal as illustrated in  FIG. 2  by cooperation of the CPU and other components on the basis of a gas supply program stored in the internal memory, and outputs a control signal to the opening and closing mechanism V 1  on the basis of these signals. 
     Hereinafter, a specific operation of the control device  20  will be described with reference to  FIGS. 4 and 5 . 
     [At Time of Exhaust Gas Analysis] 
     First, a start operation at a time of exhaust gas analysis will be described. 
     When receiving an analysis start signal input via an input interface such as a mouse, a keyboard, or a touch panel, the control device  20  outputs a control signal to the opening and closing mechanism V 1  to switch the opening and closing mechanism V 1  to a closed state (S 1  and S 2 ). 
     At this time, since the flow rate controllers are provided downstream of the analyzer X and in the recirculated channel L 2  as described above, a first flow rate A (hereinafter, referred to as an analysis gas flow rate A) as a flow rate of an analysis gas guided to the analyzer X, and a second flow rate B (hereinafter, referred to as a supply flow rate B) as a flow rate of a gas supplied from the recirculated channel L 2  to the diluter MIX become constant flow rates as shown in  FIG. 5( a ) . Note that the supply flow rate B at the time of exhaust gas analysis is a supply flow rate of the dilution gas supplied from the recirculated channel L 2  to the diluter MIX. 
     Here, as illustrated in  FIG. 5( a ) , a third flow rate C (hereinafter, referred to as a mixed gas flow rate C) as a flow rate of a mixed gas including the exhaust gas and the dilution gas flowing from the diluter to the branch point L 1  a is a flow rate obtained by adding the analysis gas flow rate A and the supply flow rate B. Since the analysis gas flow rate A and the supply flow rate B are constant flow rates as described above, the mixed gas flow rate C is also controlled to a constant flow rate. 
     A fourth flow rate D (hereinafter, referred to as a sampling flow rate D) as a flow rate of a gas sampled from the one end of the sampling channel L 1  is a flow rate of a difference between the mixed gas flow rate C and the supply flow rate B. Since the mixed gas flow rate C and the supply flow rate B are constant flow rates, the sampling flow rate D is also controlled to a constant flow rate. 
     Specifically, as illustrated in  FIG. 5( a ) , for example, a case is considered where the analysis gas flow rate A is set to  1  and the dilution gas flow rate B is set to  4 . In this case, the mixed gas flow rate C is  5  which is a sum of the analysis gas flow rate A and the dilution gas flow rate B, and the sampling flow rate D is 1 which is obtained by subtracting the dilution gas flow rate B from the mixed gas flow rate C. As a result, the exhaust gas sampled from the one end of the sampling channel L 1  is diluted five times with the dilution gas and guided to the analyzer X. 
     Thereafter, the control device  20  determines whether an analysis end signal for ending the analysis is received (S 3 ), and ends the exhaust gas analysis in a case where the analysis end signal has been received. 
     At Time of Calibration or Purge 
     Next, an operation at a time of calibration or purge will be described. The calibration or purge is preferably performed before and after the exhaust gas analysis, but may be performed either before or after the exhaust gas analysis. 
     When receiving a calibration start signal or a purge start signal input via the input interface such as a mouse, a keyboard, or a touch panel, the control device  20  outputs a control signal to the opening and closing mechanism V 1  to switch the opening and closing mechanism V 1  to an open state (S 4  and S 5 ). 
     At this time, since the flow rate controllers are provided not only downstream of the analyzer X and the recirculated channel L 2  but also in the additional channel L 3 , not only the analysis gas flow rate A and the supply flow rate B but also a fifth flow rate (hereinafter, referred to as an additional flow rate E) as a flow rate of the calibration gas or the purge gas supplied from the additional channel L 3  to the recirculated channel L 2  becomes a constant flow rate as illustrated in  FIG. 5( b ) . 
     Here, in the flow rate adjusting valve V 2  as the flow rate controller provided in the additional channel L 3 , the additional flow rate E is set to be larger than the analysis gas flow rate A. In this embodiment, since the calibration gas or the purge gas is drawn by the pump P, the additional flow rate E is smaller than the supply flow rate B. 
     Specifically, as illustrated in  FIG. 5( b ) , a case will be considered where the additional flow rate is set to 2 in a case where the analysis gas flow rate A is set to 1 and the supply flow rate B is set to 4 as in the exhaust gas analysis described above. 
     In this case, first, a sixth flow rate (hereinafter, referred to as a branch flow rate F) as a flow rate of the gas branched from the branch point L 1   a  of the sampling channel L 1  to the recirculated channel L 2  is 2 which is obtained by subtracting the additional flow rate E from the supply flow rate B. Thus, the mixed gas flow rate C becomes 3 which is a sum of the analysis gas flow rate A and the branch flow rate F. As a result, of 4 of the supply flow rate B, 3 of the mixed gas flow rate C is guided to downstream of the diluter MIX, and a seventh flow rate (hereinafter, referred to as an excess flow rate G) as a flow rate of the remaining gas is guided to upstream through the diluter MIX. That is, part of the supply flow rate B flows backward in the sampling flow rate through the diluter MIX, and the exhaust gas is not sampled. Therefore, the mixed gas at the time of calibration or purge does not include the exhaust gas, and becomes the calibration gas or the purge gas itself, and the gas supplied to the diluter MIX also becomes the calibration gas or the purge gas itself. 
     Thereafter, the control device  20  determines whether an end signal that ends the calibration or the purge is received (S 6 ), and ends the calibration or the purge in a case where the end signal has been received. 
     In this way, by switching the opening and closing mechanism V 1  to the closed state, sampling of the exhaust gas is started and the exhaust gas analysis is performed. By switching the opening and closing mechanism V 1  to the closed state, sampling of the exhaust gas is stopped and the calibration gas or the purge gas is supplied to the sampling channel L 1 . 
     In the exhaust gas analyzing device  100  according to the embodiment configured as described above, the additional channel L 3  through which the calibration gas or the purge gas flows is connected to upstream of the pump P in the recirculated channel L 2 , and thus the calibration gas or the purge gas can flow from the recirculated channel L 2  into the sampling channel L 1  with use of a negative pressure of the pump P by opening the opening and closing mechanism V 1  of the additional channel L 3 . As a result, the analyzer X can be calibrated or the sampling channel L 1  can be purged without removing the sampling probe of the sampling channel L 1  from the sampling location. 
     In addition, since the control device  20  switches the opening and closing mechanism V 1  to the open state or the closed state, the exhaust gas analysis and the calibration or purge is automatically switchable. 
     Furthermore, since the additional flow rate E is larger than the analysis gas flow rate A, and part of the calibration gas or the purge gas introduced from the additional channel L 3  into the recirculated channel L 2  flows backward through the diluter MIX in the sampling channel L 1 , the exhaust gas can be reliably prevented from flowing into the analyzer X, and calibration and purge can be appropriately performed. 
     Since the additional channel L 3  is connected between the pump P and the first filter F 1  in the recirculated channel L 2 , the dilution gas in which the particulate matter is captured from the exhaust gas flows through a connection of the additional channel L 3  at the time of exhaust gas analysis, and contamination of the additional channel L 3  can be reduced. 
     In addition, since the dehumidifier  12  is provided downstream of the pump P in the recirculated channel L 2 , the calibration gas or the purge gas can be dried and allowed to flow, and this can suppress condensation of moisture contained in these gases. 
     Note that the present invention is not limited to the embodiment. 
     For example, the connection of the additional channel L 3  is between the first filter F 1  and the pump P in the embodiment, but may be between the branch point L 1   a  and the first filter F 1  as illustrated in  FIG. 6( a ) . 
     Alternatively, as illustrated in  FIG. 6( b ) , the connection of the additional channel L 3  may connect the additional channel L 3  between the diluter MIX and the branch point L 1   a  in the sampling channel L 1  (including the diluter MIX and the branch point L 1   a  in this concept). 
     Furthermore, as shown in  FIG. 7 , in a case where the additional channel L 3  is provided with a pressure feeder B, the connection of the additional channel L 3  may be downstream of the pump P in the recirculated channel L 2 . 
     In addition, in a case where the additional channel L 3  is provided with the pressure feeder B as shown in  FIG. 8( a ) , the connection of the additional channel L 3  may be upstream of the diluter MIX in the sampling channel L 1 , or may be between the branch point L 1   a  and the analyzer X as shown in  FIG. 8( b ) . 
     The calibration start signal and the purge open signal are different signals, and the calibration and the purge can be performed as different operations. However, the calibration and the purge may be performed at once by one operation. 
     Further, the calibration gas according to the embodiment is the zero gas for the zero check, but may be, for example, a span calibration gas having a known concentration. 
     Furthermore, the opening and closing mechanism V 1  is an opening and closing valve such as an electromagnetic valve controlled by the control device  20  in the embodiment, but the opening and closing mechanism V 1  may be manually switchable to an open state or a closed state by a user. Examples of such a component include a component that is switchable to an open state or a closed state, for example, by removal of a cap provided in the additional channel L 3 . 
     Further, the additional channel L 3  may be provided with a needle valve or a flow rate control valve to adjust the additional flow rate. 
     In addition, as the exhaust gas analyzing device  100  of the present invention, the venturi as the flow rate controller  11 , the second filter F 2 , the dehumidifier  12 , and the flow rate adjusting valve V 2  as the flow rate controllers described in the embodiment are not necessary, and one, a plurality, or all of these components may be eliminated as illustrated in  FIG. 9 . In this case, the first filter F 1  may be provided upstream or downstream of the pump P in the recirculated channel L 2 . 
     In addition, the analyzer X is not limited to the CPC for measuring the number of particles of the particulate matter contained in the exhaust gas, and may measure an amount (PM) of the particulate matter. 
     The analyzer X may analyze various components contained in the exhaust gas, such as carbon monoxide (CO), carbon dioxide (CO 2 ), nitrogen oxide (NO X ), or hydrocarbon (HC). In this case, in a case where an exhaust gas cleaner such as a scrubber is provided instead of the first filter F 1  or the second filter F 2  according to the embodiment, the exhaust gas introduced into the recirculated channel L 2  can be supplied to the diluter MIX as a dilution gas. 
     The present invention is not limited to the embodiment, and it goes without saying that various modifications can be made without departing from the gist of the present invention. 
     INDUSTRIAL APPLICABILITY 
     The present invention configured as described above allows the analyzer to be calibrated or the sampling channel to be purged without removing the sampling probe from the sampling location.