On-board exhaust gas analyzer and exhaust gas analysis method

Abstract

To make it possible to accurately analyze particulate matter included in exhaust gas emitted from stop-start vehicles and hybrid vehicles, including plug-in types, this invention is made to comprise a recirculation path L2 that branches from a branching point L1a provided between an analyzer X that is provided in a sample flow path L1 through which exhaust gas from an engine E flows and a diluter MIX and joins with the diluter MIX, a pump P provided in the recirculation path L2, an additional flow path L3 that is connected to the recirculation path L2 and leads to the atmosphere, a filter F3 provided in the additional flow path L3, an opening and closing mechanism V1 provided in the additional flow path L3, an engine information acquisition unit 21 for acquiring on / off information for the engine E, an engine state determination unit 22 for determining whether the engine E is on or off, and an opening and closing control unit 23 for closing the opening and closing mechanism V1 if a determination is made that the engine E is on and opening the opening and closing mechanism V1 if a determination is made that the engine E is off.

Description

[Technical Field]

[0001] The present invention relates to an on-board exhaust gas analyzer and an exhaust gas analysis method. [Background technology]

[0002] As shown in Patent Document 1, a conventional on-board exhaust gas analyzer includes a return flow path that returns a portion of the exhaust gas flowing through the sampling flow path from the downstream side to the upstream side, and a so-called return dilution mechanism that returns the exhaust gas that flows into the return flow path to the sampling flow path as diluted gas by providing a filter in the return flow path.

[0003] When measuring particulate matter contained in engine exhaust gas using such an on-board exhaust gas analyzer, if the test vehicle is an idle-stop vehicle or a hybrid vehicle, sampling will continue even though the engine is stopped during idle-stop or electric drive, and particulate matter in the atmosphere will be guided to the analyzer and measured, compromising measurement accuracy.

[0004] On the other hand, one way to stop sampling when the engine is stopped is to stop the analyzer's sampling pump, for example. However, in this case, even if the sampling pump is started the next time the engine is started, it will not immediately reach a stable state, and the measurement accuracy immediately after the engine starts will be compromised. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Special Publication No. 2014-526679 Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, the present invention has been made to solve the above-mentioned problems in one fell swoop, and its main objective is to enable accurate analysis of particulate matter contained in exhaust gas emitted from idle-stop vehicles and hybrid vehicles. [Means for solving the problem]

[0007] In other words, the on-board exhaust gas analysis device of the present invention is characterized by comprising: a sampling flow path through which exhaust gas from an engine flows; an analyzer connected to the sampling flow path for analyzing the exhaust gas; a diluter provided upstream of the analyzer in the sampling flow path; a return flow path that branches off from a branch point set in the sampling flow path between the analyzer and the diluter and joins the diluter; a pump provided in the return flow path for directing a portion of the exhaust gas from the branch point to the diluter; an additional flow path connected to the return flow path or the sampling flow path and through which additional gas from which particulate matter has been removed flows; an opening / closing mechanism provided in the additional flow path; an engine information acquisition unit that acquires ON / OFF information that is information regarding the ON / OFF of the engine; an engine state determination unit that determines whether the engine is in an ON state or an OFF state based on the ON / OFF information; and an opening / closing control unit that closes the opening / closing mechanism when the engine state determination unit determines that the engine is in an ON state, and opens the opening / closing mechanism when the engine state determination unit determines that the engine is in an OFF state.

[0008] According to the on-board exhaust gas analyzer configured in this manner, when the engine state determination unit determines that the engine is in the OFF state, the opening / closing control unit opens the opening / closing mechanism of the additional flow path, so that the additional gas from which particulate matter has been removed can be guided from the additional flow path to the analyzer via the return flow path or the sampling flow path. This prevents particulate matter from being measured by the analyzer when the engine is switched from ON to OFF without stopping equipment downstream of the diluter, such as the analyzer's sampling pump.As a result, it becomes possible to accurately analyze particulate matter contained in exhaust gases emitted from idle-stop vehicles and hybrid vehicles.

[0009] In order to remove particulate matter from the additional gas with a simple configuration, it is preferable that an additional flow path filter for capturing particulate matter is provided in the additional flow path.

[0010] When the engine is switched from ON to OFF and the opening / closing mechanism is opened, if the additional gas introduced into the additional flow path flows back into the tailpipe of the test vehicle, the concentration of particulate matter remaining in the tailpipe will be diluted, resulting in a measurement error when the engine is then switched ON. Therefore, it is preferable that when the opening / closing control unit opens the opening / closing mechanism, the total flow rate of the additional gas flowing through the additional flow path is introduced to the analyzer. In this way, even when the engine is switched from ON to OFF and the opening / closing mechanism is opened, the additional gas introduced into the additional flow path will not flow back into the tailpipe of the test vehicle, ensuring measurement accuracy.

[0011] A specific embodiment for reliably preventing backflow is one in which, when the opening / closing control unit closes the opening / closing mechanism, the analysis gas flow rate, which is the flow rate of gas introduced into the analyzer, is controlled to a first flow rate, and when the opening / closing control unit opens the opening / closing mechanism, the additional flow rate, which is the flow rate of the additional gas flowing through the additional flow path, is controlled to the first flow rate.

[0012] In addition, in order to more reliably prevent atmospheric particulate matter from being led to the analyzer when the engine is stopped, it is preferable that when the opening / closing control unit opens the opening / closing mechanism, a portion of the additional gas flowing through the additional flow path flows back from the diluter through the sampling flow path.

[0013] To further improve measurement accuracy, it is desirable to guide the exhaust gas remaining in the tailpipe and sampling flow path to the analyzer immediately after the engine is switched from ON to OFF. Therefore, when the engine is switched from an ON state to an OFF state, it is preferable that the opening / closing control unit is configured to open the opening / closing mechanism after a predetermined first waiting time has elapsed from the time of the switch. This allows the introduction of additional gas into the analyzer to be stopped until the exhaust gas remaining in the tailpipe or sampling flow path is guided to the analyzer, thereby further improving measurement accuracy.

[0014] If the opening and closing mechanism of the additional flow path is closed immediately after the engine is switched from OFF to ON, for example, the air inside the tailpipe will be directed into the analyzer, resulting in measurement errors due to particulate matter contained in that air. Therefore, in order to reduce such measurement errors, it is preferable that when the engine is switched from an OFF state to an ON state, the opening / closing control unit is configured to close the opening / closing mechanism after a predetermined second waiting time has elapsed from the time of the switch.

[0015] A more specific configuration of the present invention is one in which the analyzer analyzes particulate matter in the exhaust gas, and the return path is provided with a return path filter that captures particulate matter.

[0016] The return path filter is preferably provided in the return path upstream of the pump. With this configuration, it is possible to reduce the amount of particulate matter flowing into the pump, thereby preventing pump failure.

[0017] It is preferable that the additional flow path is connected to the return path between the pump and the return path filter. With this configuration, during exhaust gas analysis, diluted gas containing captured particulate matter from the exhaust gas flows through the connection point of the additional flow path, thereby reducing contamination of the additional flow path.

[0018] In addition, the exhaust gas analysis method of the present invention is an exhaust gas analysis method using an on-board exhaust gas analyzer that includes a sampling flow path through which exhaust gas from an engine flows, an analyzer connected to the sampling flow path and analyzing the exhaust gas, a diluter provided upstream of the analyzer in the sampling flow path, a return flow path that branches off from a branch point set downstream of the diluter in the sampling flow path and is connected to the diluter, and a pump provided in the return flow path and that directs a portion of the exhaust gas from the branch point to the diluter, wherein the method is characterized in that an additional flow path through which additional gas from which particulate matter has been removed flows is connected to the return flow path or the sampling flow path, and an opening / closing mechanism provided in the additional flow path is closed when the engine is on and open when the engine is off. Such an exhaust gas analysis method can provide the same effects as those of the above-described on-board exhaust gas analyzer. [Effects of the Invention]

[0019] According to the present invention configured as described above, it is possible to accurately analyze particulate matter contained in exhaust gas emitted from an idle-stop vehicle or a hybrid vehicle. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic diagram showing a mode of use of an on-board exhaust gas analyzer according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram showing the configuration of the vehicle-mounted exhaust gas analyzer according to the embodiment. [Figure 3] FIG. 2 is a schematic diagram illustrating the principle of the analyzer of the embodiment. [Figure 4] 3 is a flowchart illustrating the operation of the vehicle-mounted exhaust gas analyzer according to the embodiment. [Figure 5]FIG. 2 is a schematic diagram illustrating the flow rate of gas flowing through the on-board exhaust gas analyzer of the embodiment. [Figure 6] FIG. 10 is a schematic diagram showing the configuration of an on-board exhaust gas analyzer according to another embodiment. [Figure 7] FIG. 10 is a schematic diagram showing the configuration of an on-board exhaust gas analyzer according to another embodiment. [Figure 8] FIG. 10 is a schematic diagram showing the configuration of an on-board exhaust gas analyzer according to another embodiment. [Figure 9] FIG. 10 is a schematic diagram showing the configuration of an on-board exhaust gas analyzer according to another embodiment. [Explanation of symbols]

[0021] 100...Vehicle-mounted exhaust gas analyzer 1. Exhaust gas sampling device L1: Sampling channel L2: Reflux path X...Analyzer 10. Dilution mechanism MIX...Diluter P···Pump F1: First filter 11 Flow controller L3: Additional flow path V1...Opening / closing mechanism 20 Control device DETAILED DESCRIPTION OF THE INVENTION

[0022] An embodiment of an on-board exhaust gas analyzer according to the present invention will be described below with reference to the drawings.

[0023] As shown in FIG. 1, the on-board exhaust gas analyzer 100 of this embodiment is an on-board type that is mounted on a test vehicle VH such as an idling stop vehicle or a hybrid vehicle including a plug-in type.

[0024] Specifically, as shown in FIG. 2, the on-board exhaust gas analyzer 100 includes an exhaust gas sampling device 1 that samples exhaust gas emitted from an engine E, and an analyzer X that analyzes the sampled exhaust gas.

[0025] The exhaust gas sampling device 1 samples exhaust gas from the engine E when the engine E is on (driving state) and stops sampling exhaust gas when the engine E is off (stopped state), in other words, it samples exhaust gas intermittently. Specifically, the exhaust gas sampling device 1 has an exhaust gas sampling flow path L1 with a sampling probe (not shown) attached to one end, and by attaching this sampling probe to a sampling location, for example, near the tailpipe, it samples some or all of the exhaust gas emitted from the engine E. Here, the sampling flow path L1 is partially composed of a heating pipe unit called a hot hose, and is configured to guide the sampled exhaust gas to the analyzer X while heating or maintaining it at a predetermined temperature.

[0026] The analyzer X is connected to the other end of the sampling flow path L1 and analyzes particulate matter contained in the exhaust gas, and in this case is a particle number measuring mechanism X that measures the particle number (PN) of the particulate matter.

[0027] An example of a particle number measurement mechanism is a condensation nucleus counter (CPC), as shown in Fig. 3. In this CPC, exhaust gas is introduced into a heating section A1 containing an organic gas such as isopropyl alcohol or butanol, and then cooled in a condensation section A2, causing the organic gas to condense and adhere to particulate matter in the exhaust gas, growing it to a large diameter. The grown particulate matter is then discharged through a slit A3, and the emitted particles are counted with a laser beam R. A critical orifice-type constant flow means (not shown) is provided downstream of the CPC as a flow rate controller, and a constant flow rate of gas flows through the CPC.

[0028] When using such a particle number measuring instrument X, it is necessary to dilute the exhaust gas before introducing it into the particle number measuring instrument in order to prevent the particulate matter contained in the exhaust gas from agglomerating. Note that even in analyzers X that analyze components other than the particulate matter contained in the exhaust gas, it may be necessary to dilute the exhaust gas for various reasons.

[0029] Therefore, the exhaust gas sampling device 1 of this embodiment further includes a dilution mechanism 10 for diluting the sampled exhaust gas, as shown in FIG.

[0030] The dilution mechanism 10 is a so-called reflux type that samples a portion of the exhaust gas flowing through the sampling flow path L1, removes particulate matter (measurement target) contained in the exhaust gas to produce diluted gas, and then returns the diluted gas to the sampling flow path L1.

[0031] Specifically, this dilution mechanism 10 has a return flow path L2 that branches off from a branch point L1a set on the sampling flow path L1, merges at a junction point L1b set on the sampling flow path L1, and returns a portion of the exhaust gas flowing through the sampling flow path L1 from the downstream side to the upstream side of the sampling flow path L1. In this embodiment, a diluter MIX is provided at the junction point L1b, and a branch point L1a is set between the diluter MIX and the analyzer X.

[0032] A pump P is provided in the return flow path L2 to circulate the fluid flowing in the return flow path L2, and a first return flow path filter F1 (hereinafter also referred to as the first filter F1) may be provided upstream of the pump P, i.e., between the pump P and the branch point L1a, to prevent failure of the pump P, etc., and to capture particulate matter contained in the exhaust gas.

[0033] Further, downstream of the pump P in the reflux path L2, i.e., between the pump P and the diluter MIX, there is provided a flow rate controller 11 for controlling the diluted gas flow rate, which is the flow rate of the diluted gas flowing from the reflux path L2 into the diluter MIX. The flow rate controller 11 here is a venturi as a constant flow rate means, but it may also be a mass flow controller, a flow rate adjustment valve, or the like.

[0034] Furthermore, a second return path filter F2 (hereinafter also referred to as the second filter F2) that captures particulate matter may be provided downstream of the pump P in the return path L2, i.e., between the pump P and the diluter MIX, in order to prevent particulate matter such as pump dust from being included in the diluted gas flowing into the diluter MIX. Here, the second filter F2 is provided between the pump P and the flow rate controller 11, but it may also be provided between the flow rate adjustment device 11 and the diluter MIX.

[0035] In addition, a dehumidifier 12 may be provided downstream of the pump P in the return path L2, i.e., between the pump P and the diluter MIX, to reduce the humidity of the diluted gas flowing into the diluter MIX. The dehumidifier 12 here is provided between the pump P and the second filter F2, but it may also be provided between the second filter F2 and the flow rate controller 11, between the flow rate controller 11 and the diluter MIX, or upstream of the pump P.

[0036] The on-board exhaust gas analyzer 100 of this embodiment further includes an additional flow path L3 connected upstream of the pump P in the return flow path L2, through which the additional gas from which particulate matter has been removed flows, and an opening / closing mechanism V1 provided in this additional flow path L3, and in this embodiment further includes a control device 20 that controls the opening / closing mechanism V1 to an open or closed state. Note that the term "additional gas from which particulate matter has been removed" here is not limited to gas from which particulate matter has been completely (entirely) removed, but also includes gas from which particulate matter has been removed to an extent at least less than that of the atmosphere.

[0037] In this embodiment, the additional flow path L3 has one end into which the atmosphere is introduced, and the other end connected to the upstream side (negative pressure side) of the pump P in the return flow path L2, and this additional flow path L3 is provided with a return flow path filter F3 (hereinafter also referred to as the third filter F3) that captures particulate matter contained in the atmosphere. Here, the third filter F3 is provided upstream of the opening / closing mechanism V1, but it may also be provided downstream of the opening / closing mechanism V1.

[0038] The additional flow path L3 is provided with a flow control valve V2 as a flow rate controller for adjusting the additional flow rate, which is the flow rate of the atmosphere, so that the flow rate of the atmosphere supplied from the additional flow path L3 to the return flow path L2 is constant. Note that this flow rate controller may be a mass flow controller or a plurality of venturis connected in parallel in a switchable manner.

[0039] The opening / closing mechanism V1 switches between an open state in which the atmosphere after particulate matter has been removed by the third filter F3 is supplied as additional gas from the additional flow path L3 to the return flow path L2, and a closed state in which the supply is stopped, and in this case is an opening / closing valve such as an electromagnetic valve that operates in response to a control signal from the control device 20.

[0040] The control device 20 physically comprises a CPU, internal memory, input / output interface, etc., and performs at least the functions of an engine information acquisition unit 21, an engine state determination unit 22, and an opening / closing control unit 23, as shown in Figure 2, by the CPU and other components working together based on the gas supply program stored in the internal memory.

[0041] In the following, the specific operation of the control device 20 will be described with reference to FIGS. 4 and 5, along with an explanation of each of the above-mentioned functions.

[0042] First, when exhaust gas analysis of engine E is started, engine information acquisition unit 21 acquires ON / OFF information, which is information related to the ON / OFF state of the engine (S1). This ON / OFF information indicates whether engine E is in the ON state or the OFF state, and in this embodiment, is, for example, a signal output from OBD indicating the engine state itself (ON state or OFF state). Note that other ON / OFF information may include the engine speed, engine rotation signal pulse count, fuel injection amount, etc. output from OBD, as well as information that can be acquired separately from the information from OBD, such as the exhaust gas flow rate and the concentrations of various components contained in the exhaust gas.

[0043] Next, the engine state determination unit 22 determines whether the engine is in an ON state or an OFF state based on the ON / OFF information acquired by the engine information acquisition unit 21 (S2). Specifically, the engine state determination unit 22 determines that the engine is in an ON state when the engine speed, which is the ON / OFF information, is greater than a predetermined value (e.g., zero), and determines that the engine is in an OFF state when the engine speed is equal to or less than the predetermined value (e.g., zero). The ON state is the engine state when the test vehicle VH is in engine operation, and the OFF state is the engine state when the test vehicle VH is in an idling stop or electrically driven state.

[0044] In this embodiment, the opening / closing control unit 23 is configured to control the opening / closing mechanism based on the judgment result of the engine state judgment unit 22. Specifically, if the engine state judgment unit 22 judges that the engine is in the ON state, the opening / closing mechanism V1 is closed (S3), and if the engine state judgment unit 22 judges that the engine is in the OFF state, the opening / closing mechanism V1 is opened (S4).

[0045] More specifically, the opening / closing control unit 23 here is configured to open the opening / closing mechanism V1 when the engine switches from the ON state to the OFF state, after a predetermined first waiting time has elapsed from the time when the engine state is judged by the engine state judgment unit 22 to be switched from the ON state to the OFF state. This first waiting time is set to be the time required for the exhaust gas remaining in the tailpipe or sampling flow path L1 of the test vehicle VH to be guided to the analyzer X when the engine E switches from ON to OFF, or longer than that time.

[0046] In addition, the opening / closing control unit 23 here is configured to close the opening / closing mechanism V1 when the engine switches from the OFF state to the ON state, after a predetermined second waiting time has elapsed from the time when the engine state is switched from the OFF state to the ON state by the engine state judgment unit 22. This second waiting time is set to be equal to or shorter than the time required for the exhaust gas from engine E to reach branch point L1a set on sampling flow path L1 when engine E switches from OFF state to ON state.

[0047] Thereafter, the control device 20 determines whether to end the analysis, for example, based on whether an analysis end signal has been input (S5), and if the analysis is to continue, returns to determining the engine state in S2.

[0048] [Opening and closing mechanism V1 in closed state] Next, the gas flow when it is determined that the engine is in the ON state and the opening / closing control unit 23 closes the opening / closing mechanism V1 will be described.

[0049] As described above, since flow rate controllers are provided downstream of the analyzer X and in the return path L2, when the opening / closing mechanism V1 is in the closed state, the first flow rate A (hereinafter referred to as the analysis gas flow rate A), which is the flow rate of the analysis gas introduced to the analyzer X, and the second flow rate B (hereinafter referred to as the supply flow rate B), which is the flow rate of the flowing gas supplied from the return path L2 to the diluter MIX, are constant, as shown in Figure 5(a). Note that the supply flow rate B during exhaust gas analysis is the supply flow rate of the dilution gas supplied from the return path L2 to the diluter MIX.

[0050] 5(a), the third flow rate C (hereinafter referred to as the mixed gas flow rate C), which is the flow rate of the mixed gas consisting of the exhaust gas and the dilution gas flowing from the diluter to the branch point L1a, is the sum of 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 as described above, the mixed gas flow rate C is also controlled to a constant flow rate. Furthermore, a fourth flow rate D (hereinafter referred to as sampling flow rate D), which is the flow rate of the gas sampled from one end of the sampling flow path L1, is the 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.

[0051] To explain more specifically, consider the case where the analysis gas flow rate A is set to 1 and the dilution gas flow rate B is set to 4, as shown in Figure 5(a). In this case, the mixed gas flow rate C is 5, which is the 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 the mixed gas flow rate C minus the dilution gas flow rate B. As a result, the exhaust gas sampled from one end of the sampling flow path L1 is diluted 5 times with the dilution gas and led to the analyzer X.

[0052] [Open state of opening / closing mechanism V1] Next, the gas flow when it is determined that the engine is in the OFF state and the opening / closing control unit 23 opens the opening / closing mechanism V1 will be described.

[0053] As described above, flow rate controllers are provided not only downstream of the analyzer X and in the return path L2 but also in the additional path L3. Therefore, when the opening / closing mechanism V1 is in the open state, as shown in FIG. 5(b), not only the analysis gas flow rate A and the supply flow rate B but also the fifth flow rate (hereinafter referred to as the additional flow rate E), which is the flow rate of the additional gas (i.e., air from which particulate matter has been removed) supplied from the additional path L3 to the return path L2, are constant.

[0054] In this embodiment, the flow rate adjustment valve V2, which is a flow rate controller provided in the additional flow path L3, controls the additional flow rate E to be equal to or greater than the analysis gas flow rate A introduced to the analyzer X when the engine E is ON, and in this embodiment, controls the additional flow rate E to a first flow rate equal to the analysis gas flow rate A. In this embodiment, the additional flow rate E is smaller than the supply flow rate B because the atmosphere is drawn in by the pump P.

[0055] To explain more specifically, as shown in Figure 5(b), consider the case where the analysis gas flow rate A is set to 1, the supply flow rate B is set to 4, as in the exhaust gas analysis described above, and the additional flow rate E is set to 1, which is equal to the analysis gas flow rate A.

[0056] In this case, first, the sixth flow rate (hereinafter referred to as branch flow rate F), which is the flow rate of gas branching from branch point L1a of sampling flow path L1 to return flow path L2, is 3, which is the supply flow rate B minus the additional flow rate E. As a result, the mixed gas flow rate C is 4, which is the sum of the analysis gas flow rate A and the branch flow rate F. As a result, the total flow rate (additional flow rate E) of the additional gas (air) flowing through additional flow path L3 is led to the analyzer X, and the backflow flow rate G that flows back from return flow path L2 through diluter MIX toward the test vehicle VH is essentially 0.

[0057] In this case, the mixed gas flowing through the return path L2 will be composed only of the air introduced from the additional path L3 into the return path L2, and as a result, additional gas (air) that is substantially free of particulate matter will be introduced into the analyzer X. Note that the term "gas that is substantially free of particulate matter" as used herein is a concept that includes not only gas that does not contain any particulate matter at all, but also gas that contains trace amounts of particulate matter that do not affect the measurement results of the analyzer X.

[0058] According to the vehicle-mounted exhaust gas analyzer 100 of this embodiment configured as described above, when the engine state determination unit 22 determines that the engine is in the OFF state, the opening / closing control unit 23 opens the opening / closing mechanism V1 of the additional flow path L3, so that the air introduced into this additional flow path L3 is guided to the analyzer X via the return flow path L2 with particulate matter removed by the additional flow path filter F3. This makes it possible to prevent particulate matter from being measured by analyzer X when the engine is switched from ON to OFF, without stopping equipment downstream of diluter MIX, such as the sampling pump of analyzer X. As a result, it becomes possible to accurately analyze particulate matter contained in exhaust gas emitted from idle-stop vehicles and hybrid vehicles.

[0059] Here, when the engine E switches from the ON state to the OFF state and the opening / closing mechanism V1 is opened, if the air introduced into the additional flow path L3 flows back into the tailpipe of the test vehicle VH, the concentration of particulate matter remaining in the tailpipe will be diluted, resulting in a measurement error when the engine E is subsequently switched to the ON state. In contrast, in the configuration of this embodiment, when the opening / closing control unit 23 opens the opening / closing mechanism V1, the total flow rate of the air flowing through the additional flow path L3 is led to the analyzer X. Therefore, even if the engine E switches from the ON state to the OFF state and the opening / closing mechanism is opened, the air introduced into the additional flow path L3 does not flow back into the tailpipe of the test vehicle VH, thereby ensuring measurement accuracy.

[0060] Furthermore, when the engine E switches from the ON state to the OFF state, the opening / closing control unit 23 opens the opening / closing mechanism V1 after a predetermined first waiting time has elapsed since the time of the switch. Therefore, the introduction of air into the analyzer X can be stopped until the exhaust gas remaining in the tailpipe or sampling flow path is guided to the analyzer X immediately after the engine E switches from the ON state to the OFF state, thereby further improving the measurement accuracy.

[0061] On the other hand, if the opening / closing mechanism V1 of the additional flow path L3 is closed immediately after the engine is switched from the OFF state to the ON state, the air in the tailpipe, for example, will be led to the analyzer X, resulting in a measurement error due to the particulate matter contained in the air. In contrast, in the configuration of this embodiment, when the engine E switches from the OFF state to the ON state, the opening / closing control unit 23 is configured to close the opening / closing mechanism V1 after a predetermined second waiting time has elapsed from the time of the switch, thereby reducing the above-mentioned measurement error.

[0062] Furthermore, since the additional flow path L3 is connected between the pump P and the first filter F1 in the return flow path L2, during exhaust gas analysis, diluted gas consisting of particulate matter captured from the exhaust gas flows at the connection point of the additional flow path L3, thereby reducing contamination of the additional flow path L3.

[0063] In addition, since a dehumidifier 12 is provided downstream of the pump P in the return path L2, the calibration gas and purge gas can be passed through in a dry state, thereby preventing the moisture contained in these gases from condensing.

[0064] The present invention is not limited to the above-described embodiment.

[0065] For example, in the above embodiment, the connection point of the additional flow path L3 was between the first filter F1 and the pump P, but it may also be between the branch point L1a and the first filter F1, as shown in Figure 6(a). Furthermore, as shown in Figure 6(b), the connection point of the additional flow path L3 may be between the diluter MIX and the branch point L1a in the sampling flow path L1 (a concept that includes the diluter MIX and the branch point L1a). Furthermore, as shown in FIG. 7, if a pressure-feeding means B is provided in the additional flow path L3, the connection point of the additional flow path L3 may be downstream of the pump P in the return flow path L2. In addition, as shown in Figure 8(a), if a pressure-feeding means B is provided in the additional flow path L3, the connection point of the additional flow path L3 may be upstream of the diluter MIX in the sampling flow path L1, or may be between the branch point L1a and the analyzer X, as shown in Figure 8(b).

[0066] Additionally, the on-board exhaust gas analyzer 100 according to the present invention does not necessarily require the venturi as the flow rate controller 11, the second filter F2, the dehumidifier 12, and the flow rate adjustment valve V2 as the flow rate controller described in the above embodiment, and may be configured without one, more than one, or all of these, as shown in Fig. 9. In this case, the first filter F1 may be provided upstream or downstream of the pump P in the return path L2.

[0067] In the above embodiment, the third filter F3 serving as an additional flow path filter is provided in the additional flow path L3, and gas from which particulate matter has been removed from the atmosphere is passed as the additional gas through the additional flow path L3. However, gas from which particulate matter has been removed in advance from a gas source such as a gas cylinder may also be passed as the additional gas through the additional gas flow path L3. In this case, the third filter F is not necessary.

[0068] Furthermore, in the above embodiment, the on-board exhaust gas analyzer 100 according to the present invention is configured such that when the opening / closing control unit 23 opens the opening / closing mechanism V1, the total flow rate of the air flowing through the additional flow path L3 is directed to the analyzer X. However, the on-board exhaust gas analyzer 100 may be configured such that when the opening / closing control unit 23 opens the opening / closing mechanism V1, a portion of the air flowing through the additional flow path L3 flows back from the diluter MIX through the sampling flow path L1 toward the test vehicle VH. This makes it possible to more reliably prevent atmospheric particulate matter from being led to analyzer X when engine E is stopped, and by controlling the flow rate of backflow to a small amount, it is also possible to reduce measurement errors.

[0069] Furthermore, the analyzer X is not limited to a CPC that measures the number of particles of particulate matter contained in exhaust gas, but may be one that measures the amount of particulate matter (PM). Furthermore, the analyzer X may be one that analyzes various components contained in the exhaust gas, such as carbon monoxide (CO), carbon dioxide (CO2), nitrogen oxides (NOX), and hydrocarbons (HC), and an analyzer that analyzes these components may be provided separately from the analyzer X of the above-described embodiment. In this case, if an exhaust gas cleaning device such as a scrubber is provided instead of the first filter F1 or the second filter F2 of the above-described embodiment, the exhaust gas introduced into the reflux path L2 can be supplied to the diluter MIX as a diluted gas.

[0070] Furthermore, the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications are possible without departing from the spirit of the present invention. [Industrial Applicability]

[0071] According to the present invention configured as described above, it is possible to accurately analyze particulate matter contained in exhaust gas emitted from idle-stop vehicles and hybrid vehicles including plug-in type vehicles.

Claims

1. a sampling flow path through which exhaust gas from the engine flows; an analyzer connected to the sampling flow path to analyze the exhaust gas; a diluter provided upstream of the analyzer in the sampling flow path; a return flow path that branches off from a branch point set between the analyzer and the diluter in the sampling flow path, merges with the diluter, and returns a portion of the exhaust gas flowing through the sampling flow path from the downstream side to the upstream side of the sampling flow path; a pump provided in the return path and configured to guide a portion of the exhaust gas from the branch point to the diluter; an additional flow path connected to the return flow path or the sampling flow path, through which the additional gas from which particulate matter has been removed flows; an opening / closing mechanism provided in the additional flow path; an engine information acquisition unit that acquires ON / OFF information that is information relating to ON / OFF of the engine; an engine state determination unit that determines whether the engine is in an ON state or an OFF state based on the ON / OFF information; an opening / closing control unit that closes the opening / closing mechanism when the engine state determination unit determines that the engine is in an ON state, and that opens the opening / closing mechanism when the engine state determination unit determines that the engine is in an OFF state.

2. 2. The vehicle-mounted exhaust gas analyzer according to claim 1, wherein the additional flow path is provided with an additional flow path filter for capturing particulate matter.

3. 3. The vehicle-mounted exhaust gas analyzer according to claim 1, wherein when the opening / closing control unit opens the opening / closing mechanism, the total flow rate of the additional gas flowing through the additional flow path is introduced to the analyzer.

4. an analysis gas flow rate, which is a flow rate of gas introduced into the analyzer, is controlled to a first flow rate when the opening / closing control unit closes the opening / closing mechanism; 4. The on-board exhaust gas analyzer according to claim 1, wherein when the opening / closing control unit opens the opening / closing mechanism, an additional flow rate, which is the flow rate of the additional gas flowing through the additional flow path, is controlled to the first flow rate.

5. 3. The vehicle-mounted exhaust gas analyzer according to claim 1, wherein when the opening / closing control unit opens the opening / closing mechanism, a portion of the additional gas flowing through the additional flow path flows back from the diluter through the sampling flow path.

6. 6. The on-board exhaust gas analyzer according to claim 1, wherein when the engine is switched from an ON state to an OFF state, the opening / closing control unit is configured to open the opening / closing mechanism after a predetermined first waiting time has elapsed from the time the engine is switched from an ON state to an OFF state.

7. 7. The on-board exhaust gas analyzer according to claim 1, wherein when the engine is switched from an OFF state to an ON state, the opening / closing control unit is configured to close the opening / closing mechanism after a predetermined second waiting time has elapsed from the time the engine is switched from an OFF state to an ON state.

8. the analyzer analyzes particulate matter in the exhaust gas, 8. The vehicle-mounted exhaust gas analyzer according to claim 1, wherein the return passage is provided with a return passage filter that captures particulate matter.

9. 9. The vehicle-mounted exhaust gas analyzer according to claim 8, wherein the return path filter is provided upstream of the pump in the return path.

10. 10. The vehicle-mounted exhaust gas analyzer according to claim 9, wherein the additional flow path is connected to the return flow path between the pump and the return flow path filter.

11. an analyzer for analyzing exhaust gas using an on-board exhaust gas analyzer, the analyzer comprising: a sampling flow path through which exhaust gas from an engine flows; an analyzer connected to the sampling flow path and configured to analyze the exhaust gas; a diluter provided in the sampling flow path upstream of the analyzer; a return flow path that branches off from a branch point set in the sampling flow path downstream of the diluter, joins the diluter, and returns a portion of the exhaust gas flowing through the sampling flow path from the downstream side to the upstream side of the sampling flow path; and a pump provided in the return flow path that guides a portion of the exhaust gas from the branch point to the diluter, an additional flow path through which the additional gas from which particulate matter has been removed flows is connected to the return flow path or the sampling flow path; An exhaust gas analysis method, wherein an opening / closing mechanism provided in the additional flow path is closed when the engine is in an ON state and is opened when the engine is in an OFF state.

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