JP2007278897A - Exhaust gas measuring instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To properly purify an exhaust gas introducing passage, when it is necessary to purify the exhaust gas inlet passage. <P>SOLUTION: This exhaust gas measuring instrument 10 is constituted so as to guide a part of exhaust gas into an HC analyzer 14 via the exhaust gas inlet passage 16 for measuring the concentration of the hydrocarbon component of the exhaust gas and equipped with a clean gas supply system 32, equipped with a flow amount regulation means 40, 56, 58 and 60 for regulating the amount of flow of the clean gas supplied to the gas inlet passage 16 and a heating means 38 for heating the clean gas, as necessary, to supply the clean gas regulated in its flow amount and temperature to the gas inlet passage 16 and a control means 48 for controlling the amount of flow regulation means 40, 56, 58 and 60 of the clean gas supply system 32 and the heating means 38 so as to supply a predetermined amount of flow of the clean gas to the gas inlet passage 16 at a predetermined temperature, when the exhaust gas inlet passage 17 containing the gas inlet passage 16 is purified. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an exhaust gas measuring device that extracts a part of exhaust gas of an internal combustion engine and analyzes and measures a hydrocarbon component concentration of the exhaust gas.

  The exhaust gas of automobiles contains many components that cause air pollution such as hydrocarbon components (HC) such as unburned fuel, carbon monoxide, NOx, and SOx. From the environmental aspect, it is necessary to measure the amount of these components more accurately and take measures to prevent these components from being discharged into the atmosphere.

  For example, Patent Document 1 discloses a sampling conduit for guiding exhaust gas to be measured or inspected by an automobile exhaust gas measurement device so that components in the exhaust gas can be accurately quantified or measured. In this case, a ribbon heater is wound around the tubular body that guides the exhaust gas, and the internal temperature of the tubular body is heated above the dew point temperature of the exhaust gas by heating with this ribbon heater, Aggregation is eliminated.

  Patent Document 2 discloses a gas sampling device that introduces a sample gas from a sample gas source into a gas analyzer so that a measurement component is not lost from the exhaust gas introduced into the gas analyzer. This is because the sample gas introduction pipe is connected from the inner pipe and the outer pipe so that the temperature of the sample gas introduced into the gas analyzer becomes a constant temperature regardless of the temperature of the gas discharged from the sample gas source. The sample gas flowing through the inner pipe is adjusted with heated constant temperature water flowing between the inner pipe and the outer pipe.

  Even in such an apparatus, if the exhaust gas introduction passage that guides the exhaust gas is dirty, it is difficult to perform accurate analysis and measurement of the exhaust gas. Therefore, it is conceivable to purify the exhaust gas introduction passage before the next measurement. For example, in the exhaust gas measuring device of Patent Document 3, the exhaust gas is measured in the HC concentration meter, which is one of the analyzers as described above, so that the HC concentration in the exhaust gas is accurately measured in the next measurement. Cleaning air is supplied to the introduction passage to purge the HC components remaining, adsorbed and desorbed in the exhaust gas introduction passage.

JP 2005-308710 A Japanese Utility Model Publication No. 5-71750 JP-A-6-207888

  By the way, for example, since the hydrocarbon component has a boiling point of a certain level or more, the exhaust gas introduction passage can be sufficiently purified (purged) by simply flowing the cleaning air as in the above-mentioned Patent Document 3. May be difficult.

  Therefore, an object of the present invention is to provide an exhaust gas measuring device that can appropriately purify the exhaust gas introduction passage when the exhaust gas introduction passage needs to be purified.

  In order to solve the above problems, an exhaust gas measuring apparatus according to the present invention guides a part of exhaust gas of an internal combustion engine to an HC analyzer through a gas introduction passage, and measures a hydrocarbon component concentration of the exhaust gas. An exhaust gas measuring device comprising: a flow rate adjusting means for adjusting a flow rate of a clean gas supplied to the gas introduction passage; and a heating means for heating the clean gas as necessary, wherein the flow rate and the temperature are adjusted. When purifying the clean gas supply system for supplying clean gas to the gas introduction passage and the exhaust gas introduction passage formed including the gas introduction passage, a predetermined amount of clean gas is supplied to the gas introduction passage at a predetermined temperature. And a control means for controlling the flow rate adjusting means and the heating means of the clean gas supply system so as to supply.

  According to the above configuration, when purifying the exhaust gas introduction passage formed including the gas introduction passage, a predetermined flow rate of clean gas is supplied to the gas introduction passage at a predetermined temperature. Circulates in the exhaust gas introduction passage at a predetermined temperature. As described above, when the clean gas having a predetermined flow rate flows through the exhaust gas introduction passage, components adsorbed in the exhaust gas introduction passage are appropriately removed. In addition, since the clean gas is brought to a predetermined temperature, the components adsorbed appropriately are urged to be removed and removed. That is, the exhaust gas introduction passage can be appropriately purified.

  However, it is preferable that the predetermined flow rate is a flow rate exceeding the suction flow rate of the HC analyzer, and the predetermined temperature is a temperature exceeding the analysis temperature of the HC analyzer. As a result, excessively clean air flows through the exhaust gas introduction passage, and it is possible to reliably distribute clean air throughout the exhaust gas introduction passage, so that the components adsorbed in the exhaust gas introduction passage can be removed. Will be encouraged appropriately. Furthermore, since the clean air has a temperature exceeding the analysis temperature of the HC analyzer and flows through the exhaust gas introduction passage, the separation of components adsorbed in the exhaust gas introduction passage is appropriately promoted.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Note that an exhaust gas measuring device described in the following embodiment is used for directly collecting and measuring exhaust gas on an engine bench.

  FIG. 1 is a conceptual diagram of an exhaust gas measuring apparatus 10 according to an embodiment of the present invention, and FIG. 2 is a schematic enlarged sectional view in a circle A of FIG. In FIG. 1, various pipes and the like that partition and form various passages are represented by solid lines, and electrical wiring and the like are represented by dotted lines.

  An exhaust gas (white arrow in FIG. 1) flows through the exhaust pipe 12 of the internal combustion engine (not shown), and the exhaust gas measuring device 10 is used to analyze and measure the hydrocarbon component concentration (HC concentration) of the exhaust gas. Is used. The exhaust gas measuring apparatus 10 measures the hydrocarbon component concentration in the exhaust gas of the internal combustion engine by introducing a part of the exhaust gas of the internal combustion engine to the HC analyzer 14 and analyzing it. In the present embodiment, the internal combustion engine is a diesel engine using light oil as a fuel, but the present invention may be applied to various other internal combustion engines, for example, a spark ignition internal combustion engine.

  Although not shown, the HC analyzer 14 includes a detection unit, a flow rate control unit, a pump unit, and an internal introduction passage. A suction flow rate of exhaust gas led to the HC analyzer 14 is defined by the flow rate control unit and the pump unit. Then, the exhaust gas having a flow rate suitable for the suction flow rate is guided to the internal introduction passage through the gas introduction passage 16 for analysis. In the present specification, in order to measure the hydrocarbon component concentration of the exhaust gas, the passage through which the exhaust gas is led is collectively referred to as “exhaust gas introduction passage” 17. Specifically, the exhaust gas introduction passage 17 includes a gas introduction passage 16 and an internal introduction passage of the HC analyzer 14.

  By the way, since the hydrocarbon component in the exhaust gas has a boiling point of about 200 ° C., in order to be introduced to the HC analyzer 14 in a vaporized state, the exhaust gas is at 191 ° C. ± 20 ° C., for example. It is necessary that the temperature be maintained. Therefore, the extracted exhaust gas is adjusted to such a temperature and used for analytical measurement, as will be described later.

  A gas introduction pipe 18 that defines the gas introduction passage 16 connects the exhaust pipe 12 and the HC analyzer 14 in order to introduce a part of the exhaust gas to the HC analyzer 14. The gas introduction pipe 18 includes a heating unit 22 that is heated by a heater 20 as temperature adjusting means, and a non-heating unit 24 that is not heated by the heater 20. The heating unit 22 extends from the outer surface of the exhaust pipe 12 to the HC analyzer 14 on the downstream side, and the heater 20 is disposed in this section. The heater 20 heats and keeps the heating unit 22 so that the temperature of the gas passing through the heating unit 22 is adjusted to around 200 ° C. The heater 20 is a ribbon heater and is wound around the gas introduction pipe 18, but the present invention does not exclude other temperature control means.

  The non-heating portion 24 of the gas introduction pipe 18 is positioned in the exhaust pipe 12 so as to extract a part of the exhaust gas appropriately without going against the flow. As is apparent from FIG. 1, the opening 28 of the non-heating unit 24 opens toward the upstream side of the exhaust pipe 12. Therefore, the axis of the gas introduction pipe 18 in the vicinity of the opening 28 is substantially parallel to the axis of the exhaust pipe 12.

  As shown in FIG. 2, a reduced diameter portion 30 for reducing the diameter of the gas introduction passage 16 is provided in the non-heating portion 24 of the gas introduction pipe 18. The reduced diameter portion 30 constitutes a so-called orifice. The reduced diameter portion 30 is positioned in the vicinity of the opening portion 28, and functions to increase the flow rate of the exhaust gas guided from the opening portion 28 to the gas introduction passage 16 and decrease the pressure thereof.

  Further, the exhaust gas measuring device 10 is provided with a clean gas supply system 32 in order to control the temperature of the exhaust gas to the HC analyzer 14 more reliably. The clean gas supply system 32 heats clean gas, that is, clean air that does not contain hydrocarbon components stored in the tank 34 in the present embodiment, to a predetermined temperature while adjusting the flow rate to a predetermined flow as necessary. , A configuration that enables supply to the gas introduction passage 16 is provided. Specifically, the clean gas supply system 32 includes a tank 34, a supply pipe 36 that connects the tank 34 and the non-heating unit 24, and a heating unit that heats the clean gas flowing through the supply pipe 36 as necessary. 38 and a flow rate control means 40 for adjusting and controlling the flow rate of the clean gas flowing through the clean gas supply system 30. The supply pipe 36 is the non-heated part 24 and is downstream of the maximum diameter reduction part 30 a of the diameter reducing part 30 so that the clean gas supply system 32 can supply clean gas to the upstream end part of the gas introduction passage 16. It is connected to the gas introduction pipe 18 on the side. In the present embodiment, as shown in FIG. 2, the opening 36 a of the supply pipe 36 is positioned immediately downstream of the reduced diameter portion 30.

  The supply pipe 36 has a structure in which it is divided into two systems on the way and merged again. Here, in the supply pipe 36, the upstream part which is one system connected to the tank 34 is the upstream part 42, and the downstream part which is one system connected to the non-heating part 24 of the gas introduction pipe 18 is downstream. The intermediate portion formed of two systems sandwiched between the upstream portion 42 and the downstream portion 44 is referred to as a midstream portion 46. The upstream portion 42 is provided with a flow rate control means 40, and the flow rate control means 40 is controlled by a control device 48 described later. Specifically, the flow control means 40 is a so-called regulator. The two systems of the midstream portion 46 include a heating system 50 and a non-heating system 52, and the heating system 50 is provided with a heating means 38. The heating means 38 controlled by the control device 48 is a ribbon heater as with the heater 20 as the temperature adjusting means, but may be other heating means. Further, the downstream portion 44 is provided with a two-way control valve 56 for closing or opening the supply pipe 36. In addition, three-way control valves 58 and 60 are provided at the connecting portion between the upstream portion 42 and the midstream portion 46 and at the connecting portion between the midstream portion 46 and the downstream portion 44, respectively. As a result, the clean gas heated by passing through the heating system 50 (hereinafter referred to as heated clean gas) and the clean gas at room temperature that is not heated by passing through the non-heated system 52 are introduced into the gas introduction passage 16. (Hereinafter referred to as room temperature clean gas) can be selectively supplied. In the present embodiment, the flow rate control means 40 and the control valves 56, 58, 60 constitute a flow rate adjustment means.

  The exhaust gas measurement device 10 includes a temperature sensor 62 for detecting the temperature of the exhaust gas itself guided to the gas introduction passage 16. The temperature sensor 62 is the non-heating unit 24 and is provided on the downstream side of the reduced diameter portion 30 and the downstream side of the connection portion of the supply pipe 36.

  Further, the exhaust gas measuring device 10 includes a temperature sensor 64 for detecting the temperature of the clean gas supplied from the tank 34 to the upstream portion 42 of the supply pipe 36. In the present embodiment, the temperature sensor 64 is provided in a portion of the upstream portion 42 on the downstream side of the flow rate control means 40. Hereinafter, the temperature sensor 62 provided in the gas introduction pipe 18 is referred to as a first temperature sensor, and the temperature sensor 64 provided in the supply pipe 36 is referred to as a second temperature sensor.

  The exhaust gas measuring device 10 includes a control device 48. The control device 48 is configured to include the function of the control means. The control device 48 includes a computer including a CPU, ROM, RAM, A / D converter, input interface, output interface, and the like. The HC analyzer 14 and the first and second temperature sensors 62 and 64 are electrically connected to the input interface. Based on the output signals from the first and second temperature sensors 62 and 64, the control device 48 is electrically connected from the output interface so that the hydrocarbon component concentration of the exhaust gas is measured according to a preset program. A signal is output to control the operation of the heater 20, the heating means 38, the flow rate control means 40, and the control valves 56, 58, and 60.

  First, the measurement of the hydrocarbon component concentration in the exhaust gas in the present embodiment will be schematically described. If the temperature ET of the exhaust gas introduced into the gas introduction passage 16 is within a predetermined range, the exhaust gas is introduced to the HC analyzer 14 as it is, and the exhaust gas measurement device 10 measures the hydrocarbon component concentration. On the other hand, if the temperature ET of the exhaust gas led to the gas introduction passage 16 is not within the predetermined range, the exhaust gas measurement device 10 supplies the clean gas from the clean gas supply system 32 to the gas introduction passage 16 and the exhaust gas thereof. While adjusting the temperature of the gas to a predetermined range temperature, the gas is led to the HC analyzer 14 and the concentration of the hydrocarbon component is measured. That is, when the exhaust gas has a temperature equal to or higher than the upper limit temperature UT of the predetermined range temperature, the room temperature clean gas is supplied to the gas introduction passage 16 and mixed with the exhaust gas to adjust the temperature. On the contrary, when the exhaust gas has a temperature equal to or lower than the lower limit temperature DT of the predetermined range temperature, the heated clean gas is supplied to the gas introduction passage 16 and mixed with the exhaust gas to adjust the temperature. .

  Below, the measurement of the hydrocarbon component concentration in the exhaust gas by the exhaust gas measuring device 10 having the above configuration will be described based on the flowchart of FIG. However, in the exhaust gas measuring device 10, although not described in detail, the analysis by the HC analyzer 14 is continuously performed while the power source of the exhaust gas measuring device 10 is turned on by a tester or the like. The analysis value from the analyzer 14 is sent to the control device 48. Then, what is represented in the flowchart of FIG. 3 is the control for introducing the temperature-controlled exhaust gas to the HC analyzer 14. The control device 48 corrects the analysis value sent from the HC analyzer 14 as necessary to obtain a measured value of the hydrocarbon component concentration of the exhaust gas.

  In the HC analyzer 14, as described above, the exhaust gas suction flow rate through the gas introduction passage 16 is substantially constant, and a predetermined flow rate of exhaust gas is extracted through the gas introduction passage 16 to be extracted. 14 for analysis. In this state, in step S301, the temperature ET of the exhaust gas guided to the gas introduction passage 16 is detected. The detection of the exhaust gas temperature ET is performed by the first temperature sensor 62. Here, the following description will be continued assuming that the detected exhaust gas temperature ET is 200 ° C.

  Next, in step S303, the temperature CT of the clean gas stored in the tank 34 is detected. The detection of the temperature CT of the clean gas is performed by the second temperature sensor 64. Here, the following description will be continued assuming that the detected temperature CT of the clean gas is 25 ° C.

  Then, the process proceeds to step S305, and it is determined whether or not the temperature ET of the exhaust gas detected in step S301 is a temperature within a predetermined range temperature that should be referred to as an analysis temperature in the HC analyzer 14. In the present embodiment, the predetermined range temperature is 191 ° C. ± 20 ° C., and is defined so as not to include the upper limit temperature UT and the lower limit temperature DT, which are the temperatures at the boundary. The upper limit temperature UT is 211 ° C., and the lower limit temperature DT is 171 ° C. In step S305, it is determined whether or not the detected exhaust gas temperature ET is equal to or higher than the upper limit temperature UT. Here, since the exhaust gas temperature ET is 200 ° C., the determination is negative, and the process proceeds to step S307.

  In step S307, it is determined whether or not the detected exhaust gas temperature ET is equal to or lower than the lower limit temperature DT. Here, since the temperature ET of the exhaust gas is 200 ° C., the determination is negative and the process proceeds to step S309. In step S309, in order to stop the supply of the clean gas from the clean gas supply system 32 to the gas introduction passage 16, an operation signal is output to the flow rate control means 40 so as to set the clean gas supply amount to "0". An operation signal is output to an actuator (not shown) that operates the control valves 56, 58, and 60 so as to be closed. It is sufficient that at least the control valve 56 is closed and the supply of clean gas is stopped.

  As described above, if the exhaust gas temperature ET is a temperature within the predetermined range, the extracted exhaust gas is directly introduced to the HC analyzer 14 as described above, and the hydrocarbon component concentration is analyzed. Then, the analysis value is sent to the control device 48 as it is and recorded or used as the hydrocarbon component concentration of the exhaust gas.

  On the other hand, for example, the case where the temperature ET of the exhaust gas is outside the predetermined range temperature and is equal to or higher than the upper limit temperature UT will be described below. Specifically, the following description will be made assuming that the exhaust gas temperature ET detected by the first temperature sensor 62 is 700 ° C. It is assumed that the temperature CT of the clean gas detected by the second temperature sensor 64 is 25 ° C.

  In step S301, the exhaust gas temperature ET is detected. In step S303, the clean gas temperature CT is detected. In step S305, the exhaust gas temperature ET is determined to be equal to or higher than the upper limit temperature UT, and the process proceeds to step S311. When step S311 is reached, the control device 48 performs control to flow the normal temperature clean gas so as to lower the temperature ET of the exhaust gas guided to the gas introduction passage 16 and adjust the temperature to a predetermined range temperature. First, at step S311, the control device 48 obtains an experiment in advance based on the exhaust gas temperature ET detected at step S301 and the clean gas temperature CT detected at step S303, and stores the map in the ROM. To derive the flow rate of the room temperature clean gas. Then, the control valve 56 is opened so that the normal temperature clean gas of this flow rate is supplied to the gas introduction passage 16 via the non-heating system 52 of the midstream portion 46 of the supply pipe 36, and the upstream portion 42 and the midstream portion 46 are not connected. The control valve 58 is opened so that the heating system 52 is communicated, the control valve 60 is opened so that the downstream part 44 and the non-heating system 52 of the midstream part 46 are communicated, and the flow rate of the normal temperature clean gas The flow rate control means 40 is controlled so as to be adjusted. As a result, a room temperature clean gas having a predetermined flow rate is supplied to the gas introduction passage 16.

  Here, the flow rate of the supplied room temperature clean gas will be described. In the gas introduction passage 16, the normal temperature clean gas is mixed so that the exhaust gas and the normal temperature clean gas supplied to the exhaust gas are mixed and the temperature of the exhaust gas analyzed by the HC analyzer 14 is adjusted to the temperature within the predetermined range. The flow rate of is required. For example, as described above, when the exhaust gas temperature ET is 700 ° C. and the normal temperature clean gas temperature is 25 ° C., the ratio of the normal temperature clean gas flow rate to the exhaust gas flow rate is about 3: 1 (clean The flow rate of the normal temperature clean gas is determined so that the gas flow rate is equal to the exhaust gas flow rate. Then, the flow rate control means 40 and the like are controlled by the control device 48 as described above so that the flow rate of the room temperature clean gas is realized, so that the exhaust gas is set at 194 ° C., for example.

  As described above, the reduced diameter portion 30 is provided in the non-heated portion 24 of the gas introduction pipe 18, and the room temperature clean gas is provided in the non-heated portion 24 downstream of the maximum reduced diameter portion 30 a of the reduced diameter portion 30. Therefore, the normal temperature clean gas is appropriately sucked into the gas introduction passage 16 by the ejector (mist spraying) effect by the exhaust gas whose pressure has become low (see FIG. 4). Furthermore, as the exhaust gas that has passed through the reduced diameter portion 30 spreads to the gas introduction passage 16 having a large cross-sectional area, the room temperature clean gas sucked into the gas introduction passage 16 is appropriately diffused into the exhaust gas, The mixing effect that the exhaust gas and the room temperature clean gas are reliably mixed in the portion 24 is exhibited. Then, the temperature of the mixed exhaust gas can be appropriately detected by the first temperature sensor 62, and the control device 48 can feedback control the flow rate control means 40 and the like. The mixed exhaust gas has a uniform composition and reaches the HC analyzer 14. Since the ejector effect and the mixing effect as described above prevent the normal temperature clean gas from flowing back into the exhaust pipe 12, the normal temperature clean gas is effectively used for adjusting the temperature of the exhaust gas. Become.

  On the other hand, for example, the case where the temperature ET of the exhaust gas is outside the predetermined range temperature and below the lower limit temperature DT will be described below. Specifically, the following description will be made assuming that the exhaust gas temperature ET detected by the first temperature sensor 62 is 25 ° C. It is assumed that the temperature CT of the clean gas detected by the second temperature sensor 64 is 25 ° C.

  In step S301, the exhaust gas temperature ET is detected. In step S303, the clean gas temperature CT is detected. In step S305, it is denied that the exhaust gas temperature ET is not equal to or higher than the upper limit temperature UT, and the process proceeds to step S307. It is determined that the exhaust gas temperature ET is equal to or lower than the lower limit temperature DT, and the process proceeds to step S313. In step S313, the heated clean gas is flowed in order to raise the temperature ET of the exhaust gas guided to the gas introduction passage 16 and adjust the temperature to a predetermined range temperature. First, at step S313, the control device 48 obtains an experiment in advance based on the exhaust gas temperature ET detected at step S301 and the clean gas temperature CT detected at step S303, and stores the map in the ROM. (A map different from the map used when step S311 is reached) is searched to derive the temperature and flow rate of the heated clean gas. Then, the control valve 56 is opened so that the heated clean gas having this temperature and flow rate is supplied to the gas introduction passage 16 via the heating system 50 of the midstream portion 46 of the supply pipe 36, and the upstream portion 42 and the midstream portion 46. The control valve 58 is opened so that the heating system 50 communicates, and the control valve 60 is opened so that the downstream system 44 communicates with the heating system 50 of the midstream part 46, and the flow rate of the heated clean gas is adjusted. Thus, the flow rate control means 40 is controlled, and the heating means 38 is controlled so that the temperature of the heated clean gas is adjusted. As a result, the heated clean gas having a predetermined flow rate and a predetermined temperature is supplied to the gas introduction passage 16.

  Here, the temperature and flow rate of the supplied heated clean gas will be described. In the gas introduction passage 16, the flow rate and temperature of the heated clean gas are determined so that the exhaust gas and the heated clean gas supplied thereto are mixed and the temperature of the exhaust gas is adjusted to the predetermined range temperature. For example, when the exhaust gas temperature ET and the clean gas temperature are both 25 ° C. as described above, a temperature of 250 ° C. is required as the heated clean gas temperature. The flow rate of the heated clean gas is determined so that the ratio between the flow rate of the heated clean gas and the flow rate of the exhaust gas is about 3: 1 (clean gas flow rate: exhaust gas flow rate). Then, as described above, the flow rate control means 40, the heating means 38, and the like are controlled by the control device 48 so that the flow rate and temperature of the heated clean gas are realized. Note that the heated clean gas adjusted to such a flow rate and temperature mixes with the exhaust gas in the gas introduction passage 16 as described above, for example, reaches 194 ° C. and reaches the HC analyzer 14 appropriately. Become.

  As described above, when the temperature of the exhaust gas is not within the predetermined range, the clean gas is supplied to the gas introduction passage 16 as a normal temperature clean gas or a heated clean gas and mixed with the exhaust gas for analysis. However, since the clean gas is mixed with the exhaust gas and the exhaust gas is diluted to analyze the hydrocarbon component concentration, the analysis value is not a value for the exhaust gas itself. Therefore, the control device 48 corrects the analysis value from the HC analyzer 14 in accordance with the supply amount of the supplied clean gas and derives the measurement value.

  As described above, when supplying the clean gas, the flow rate control means 40 is controlled so that the ratio of the flow rate of the clean gas and the flow rate of the exhaust gas becomes a predetermined ratio such as 3: 1. Therefore, based on the predetermined ratio, the control device 48 retrieves data previously obtained through experiments and stored in the ROM, derives a correction coefficient, and analyzes from the HC analyzer 14 based on the correction coefficient. The value is to be corrected. The clean gas supply point is the heating unit 24 that is the upstream end portion of the gas introduction pipe 18 and is away from the HC analyzer 14, so that the supply timing of the clean gas from the clean gas supply system 32 and the HC There is a time difference from the analysis time in the analyzer 14. Therefore, although not described in detail, the control device 48 corrects the analysis value by eliminating the time difference based on the results obtained in advance by experiments. Therefore, it becomes possible to appropriately analyze the exhaust gas of the internal combustion engine under all operating conditions. That is, the hydrocarbon component concentration of the exhaust gas can be measured continuously and accurately under all operating conditions.

  In this way, the exhaust gas is temperature-controlled and guided to the HC analyzer 14, and the measured value is derived by correcting the analytical value as necessary, so that the length of the gas introduction passage 16 is predetermined as shown in FIG. Can be of length. If the clean gas supply system 32 is not provided, in order to make it possible to analyze exhaust gas at any temperature, for example, a portion of a certain length of the gas introduction pipe 18 continuing from the exhaust pipe 12 is used as a cooling path. In addition, it is necessary to further include a heating path provided with heating means for heating the exhaust gas sufficiently cooled in the cooling path to the analysis temperature. However, by applying the present invention, it is not necessary to provide at least such a cooling path, and the length of the gas introduction passage 16 reaching the HC analyzer 14 can be shortened.

  Although the exhaust gas analysis measurement in the exhaust gas measurement device 10 has been described above based on the embodiment, the present invention is not limited thereto. For example, whether or not to supply clean gas to the exhaust gas is determined by whether or not the temperature of the exhaust gas is not a predetermined range temperature having a certain width, the predetermined range temperature is a temperature having no width, For example, it may be 200 ° C. In this case, it is preferable to supply a normal temperature clean gas when the temperature of the exhaust gas exceeds 200 ° C., and supply a heated clean gas when the temperature of the exhaust gas is lower than 200 ° C. The supply of the clean gas at that time is preferably performed in the same manner as described with respect to steps S311 and S313. Moreover, in the said embodiment, the gas introduction pipe 18 is good also as only a non-heating part, ie, the gas introduction pipe 18 does not need to be heated at all by the temperature control means such as the heater 20. This is because the exhaust gas is appropriately adjusted to the analysis temperature by supplying the room temperature clean gas or the heated clean gas as described above. However, it is not excluded that the temperature adjusting means is provided as described above in order to adjust the temperature of the exhaust gas to the HC analyzer 14 more appropriately. Further, in the above embodiment, the supply pipe of the clean gas supply system 32 is divided into two systems in the middle, and one of them is provided with the heating means 38 so that the normal temperature clean gas and the heated clean gas can be selectively supplied. However, the supply pipe may consist of one system. In this case, a heating means is provided in the middle of the one supply pipe, and heating by the heating means is performed only when it is desired to supply the heated clean gas, thereby selectively supplying the heated clean gas and the room temperature clean gas. Is possible.

  By the way, when the internal combustion engine that examines the exhaust gas is replaced with another one, or when analyzing and measuring the exhaust gas under different operating conditions in the same internal combustion engine, the hydrocarbon component concentration of the exhaust gas is continuously analyzed. When attempting to measure, the influence of the previous analysis measurement does not necessarily have to occur in the measurement values after the next time. Therefore, in such a case, the exhaust gas introduction passage 17 formed including the gas introduction passage 16 is purified, that is, purged, in order to greatly reduce the influence of the previous analysis measurement. The purification of the exhaust gas introduction passage 17 will be described below.

  As described above, when the hydrocarbon component concentration of the exhaust gas is measured, the exhaust gas is heated to a temperature close to 200 ° C. in the gas introduction passage 16, so that the hydrocarbon component in the exhaust gas is generally vaporized. Most of them will be subjected to analysis by the HC analyzer 14. However, hydrocarbon components in the exhaust gas may be adsorbed on the exhaust gas introduction passage 17, for example, the inner wall surface of the gas introduction pipe 18. Some of the adsorbed hydrocarbon components may be desorbed during the analytical measurement, but may continue to be adsorbed on the inner wall surface of the gas introduction pipe 18 until the next analytical measurement of the exhaust gas.

  Therefore, the heated clean gas is supplied to the exhaust gas introduction passage 17 to purify the passage 17 so that the adsorbed hydrocarbon components do not adversely affect the next analysis measurement. By the control of the flow rate control means 40 and the heating means 38 of the clean gas supply system 32 of the control device 48, the clean gas with a predetermined flow rate is supplied at a predetermined temperature.

  The “predetermined flow rate” here is a flow rate that exceeds the suction flow rate of the HC analyzer, and is stored in advance in the ROM. Therefore, the clean gas supplied into the gas introduction pipe 18 overflows and flows not only to the HC analyzer 14 side but also to the exhaust pipe 12 side beyond the reduced diameter portion 30 (see FIG. 5). . Therefore, the entire exhaust gas introduction passage 17 including the gas introduction passage 16 is appropriately purified.

  Further, the “predetermined temperature” is an analysis temperature in the HC analyzer 14, that is, a temperature exceeding the predetermined range temperature, and is stored in the ROM in advance. Therefore, the clean gas supplied to the exhaust gas introduction passage 17 is a heated clean gas, which promotes desorption of adsorbed hydrocarbon components and the like. However, this predetermined temperature is preferably in the range of 200 ° C. or more and 250 ° C. or less. The control from the control device 48 to the heating unit 38 at this time may be performed based on the clean gas temperature CT detected by the second temperature sensor 64.

  As described above, the heated clean gas having a predetermined temperature exceeding the predetermined temperature range that is the analysis temperature is supplied to the gas introduction passage 16 at a predetermined flow rate that exceeds the suction flow rate of the HC analyzer 14, and the exhaust gas introduction passage 17 is passed through the exhaust gas introduction passage 17. The hydrocarbon components adsorbed on the exhaust gas introduction passage 17, for example, the inner wall surface of the gas introduction pipe 18, are appropriately generated by the dynamic force of the heated clean gas and the chemical action by the heat of the heated clean gas. Will be removed. Therefore, the next analysis and measurement of the hydrocarbon component concentration of the exhaust gas can be performed more accurately.

  Even if the purification of the gas introduction pipe 18 and the like is not completely performed by the purification as described above, the exhaust gas introduction passage 17 is purified by the heated clean gas so that the HC analyzer 14 Even when the exhaust gas adjusted to the analysis temperature reaches the exhaust gas introduction passage 17, the desorption of the remaining hydrocarbon components is suppressed to the minimum. Therefore, the analytical measurement of the hydrocarbon component concentration of the exhaust gas can be performed appropriately.

  In addition, when the hydrocarbon components adsorbed on the inner wall surface of the gas introduction pipe 18 are not sufficiently removed by the purification as described above, and the adsorbed hydrocarbon components are desorbed in the subsequent analysis measurement, The clean gas is heated to the analysis temperature and supplied into the gas supply pipe 18, the hydrocarbon component concentration of the clean gas is analyzed and measured by the HC analyzer 14, and the analyzed value is corrected as a reference value. Also good. For example, such an analytical value (hereinafter referred to as a standard analytical value) is obtained before the next analytical measurement, and correction is performed by excluding the standard analytical value from the analytical value in the subsequent exhaust gas analytical measurement. Thus, the hydrocarbon component concentration in the exhaust gas can be appropriately measured.

  As mentioned above, although this invention was demonstrated based on the said embodiment, this invention is not limited to it. For example, in the above-described embodiment, the exhaust gas measuring device is used for directly collecting and measuring exhaust gas on an engine bench. However, the exhaust gas measuring device may be mounted on a traveling vehicle and similarly used for analyzing and measuring exhaust gas. . Then, the measured value may be used to control the internal combustion engine of the running vehicle.

  In the above embodiment, clean air containing no hydrocarbon component is used as the clean gas, but nitrogen gas or the like may be used. In addition, when a gas containing a hydrocarbon component is used as the clean gas, the hydrocarbon component concentration is measured in advance, and the hydrocarbon component concentration of the exhaust gas is obtained by subtracting it from the measured value. Also good. In the above embodiment, the clean gas is stored in the tank 34. However, the air around the exhaust gas measuring device 10 may be used as the clean gas. Furthermore, in the above embodiment, the temperature of the clean gas guided to the supply pipe 36 is detected and the clean gas supply system 32 is controlled based on the detected temperature. However, the temperature is not based on the temperature of the clean gas. It may be controlled. In this case, the second temperature sensor 64 can be omitted.

1 is a conceptual diagram of an exhaust gas measuring device according to an embodiment of the present invention. It is an expanded sectional view in the circle A of FIG. It is an example of the flowchart for adjusting temperature of exhaust gas. It is the figure which represented typically the flow of the clean gas during exhaust gas analysis. It is the figure which represented typically the flow of the clean gas during exhaust gas introduction channel | path purification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Exhaust gas measuring device 12 Exhaust pipe 14 HC analyzer 16 Gas introduction path 17 Exhaust gas introduction path 18 Gas introduction pipe 20 Heater 22 Heating part 24 Non-heating part 26 Exhaust path 28 Opening part 30 Reduced diameter part 32 Clean gas supply system 34 Tank 36 Supply pipe 38 Heating means 40 Flow rate control means 48 Control device

Claims (2)

An exhaust gas measuring device for guiding a part of exhaust gas of an internal combustion engine to an HC analyzer through a gas introduction passage and measuring a hydrocarbon component concentration of the exhaust gas,
A flow rate adjusting means for adjusting the flow rate of the clean gas supplied to the gas introduction passage; and a heating means for heating the clean gas as required. The clean gas having the flow rate and temperature adjusted is supplied to the gas introduction passage. A clean gas supply system to supply;
When purifying the exhaust gas introduction passage formed including the gas introduction passage, the flow rate adjusting means of the clean gas supply system and the flow rate adjusting means of supplying a predetermined flow rate of clean gas to the gas introduction passage at a predetermined temperature, and Control means for controlling the heating means;
An exhaust gas measuring device comprising: The predetermined flow rate is a flow rate exceeding the suction flow rate of the HC analyzer,
The exhaust gas measuring device according to claim 1, wherein the predetermined temperature is a temperature exceeding an analysis temperature in the HC analyzer.

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